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	$106.97	3.680%	$110.9065	$110.91	$110.90	$110.90
Purchase #2	$124.64	5.409%	$131.3818	$131.38	$131.40	$131.40
Purchase #3	$99.99	9.227%	$109.2161	$109.22	$109.20	$109.20
Purchase #4	$65.44	6.779%	$69.8762	$69.88	$69.90	$69.90
Purchase #5	$207.36	12.389%	$233.0498	$233.05	$233.05	$233.00
Purchase #6	$106.62	4.315%	$111.2207	$111.22	$111.20	$111.20
Purchase #7	$245.49	3.406%	$253.8514	$253.85	$253.85	$253.90
7 purchase totals =	$956.51		$1,019.5025	$1,019.51	$1,019.50	$1,019.50