Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.42	4.317%	$178.8202	$178.82	$178.80	$178.80
Purchase #2	$116.28	11.789%	$129.9882	$129.99	$130.00	$130.00
Purchase #3	$240.35	10.573%	$265.7622	$265.76	$265.75	$265.80
Purchase #4	$154.54	9.330%	$168.9586	$168.96	$168.95	$169.00
Purchase #5	$99.72	11.576%	$111.2636	$111.26	$111.25	$111.30
Purchase #6	$161.82	12.718%	$182.4003	$182.40	$182.40	$182.40
Purchase #7	$116.92	6.793%	$124.8624	$124.86	$124.85	$124.90
7 purchase totals =	$1,061.05		$1,162.0555	$1,162.05	$1,162.00	$1,162.20