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	$154.81	4.736%	$162.1418	$162.14	$162.15	$162.10
Purchase #2	$122.59	4.491%	$128.0955	$128.10	$128.10	$128.10
Purchase #3	$90.54	9.554%	$99.1902	$99.19	$99.20	$99.20
Purchase #4	$154.57	10.828%	$171.3068	$171.31	$171.30	$171.30
Purchase #5	$47.71	12.680%	$53.7596	$53.76	$53.75	$53.80
Purchase #6	$23.76	11.374%	$26.4625	$26.46	$26.45	$26.50
Purchase #7	$124.64	12.463%	$140.1739	$140.17	$140.15	$140.20
7 purchase totals =	$718.62		$781.1303	$781.13	$781.10	$781.20