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	$181.77	3.557%	$188.2356	$188.24	$188.25	$188.20
Purchase #2	$174.52	9.351%	$190.8394	$190.84	$190.85	$190.80
Purchase #3	$121.37	5.561%	$128.1194	$128.12	$128.10	$128.10
Purchase #4	$40.40	8.307%	$43.756	$43.76	$43.75	$43.80
Purchase #5	$58.52	7.487%	$62.9014	$62.90	$62.90	$62.90
Purchase #6	$116.27	13.258%	$131.6851	$131.69	$131.70	$131.70
Purchase #7	$242.81	8.360%	$263.1089	$263.11	$263.10	$263.10
7 purchase totals =	$935.66		$1,008.6458	$1,008.66	$1,008.65	$1,008.60