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	$180.69	5.180%	$190.0497	$190.05	$190.05	$190.00
Purchase #2	$122.56	5.653%	$129.4883	$129.49	$129.50	$129.50
Purchase #3	$142.50	5.442%	$150.2549	$150.25	$150.25	$150.30
Purchase #4	$247.90	8.843%	$269.8218	$269.82	$269.80	$269.80
Purchase #5	$121.28	8.513%	$131.6046	$131.60	$131.60	$131.60
Purchase #6	$29.86	13.571%	$33.9123	$33.91	$33.90	$33.90
Purchase #7	$103.69	9.822%	$113.8744	$113.87	$113.85	$113.90
7 purchase totals =	$948.48		$1,019.0060	$1,018.99	$1,018.95	$1,019.00