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	$227.37	11.492%	$253.4994	$253.50	$253.50	$253.50
Purchase #2	$238.58	10.559%	$263.7717	$263.77	$263.75	$263.80
Purchase #3	$92.50	7.493%	$99.431	$99.43	$99.45	$99.40
Purchase #4	$5.89	4.245%	$6.14	$6.14	$6.15	$6.10
Purchase #5	$231.92	3.114%	$239.142	$239.14	$239.15	$239.10
Purchase #6	$82.72	9.107%	$90.2533	$90.25	$90.25	$90.30
Purchase #7	$93.91	5.695%	$99.2582	$99.26	$99.25	$99.30
7 purchase totals =	$972.89		$1,051.4956	$1,051.49	$1,051.50	$1,051.50