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	$147.86	5.695%	$156.2806	$156.28	$156.30	$156.30
Purchase #2	$114.60	12.462%	$128.8815	$128.88	$128.90	$128.90
Purchase #3	$222.76	11.421%	$248.2014	$248.20	$248.20	$248.20
Purchase #4	$53.84	12.524%	$60.5829	$60.58	$60.60	$60.60
Purchase #5	$220.34	4.333%	$229.8873	$229.89	$229.90	$229.90
Purchase #6	$99.28	10.588%	$109.7918	$109.79	$109.80	$109.80
Purchase #7	$132.27	3.823%	$137.3267	$137.33	$137.35	$137.30
7 purchase totals =	$990.95		$1,070.9522	$1,070.95	$1,071.05	$1,071.00