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	$236.80	9.235%	$258.6685	$258.67	$258.65	$258.70
Purchase #2	$238.61	7.424%	$256.3244	$256.32	$256.30	$256.30
Purchase #3	$173.93	4.740%	$182.1743	$182.17	$182.15	$182.20
Purchase #4	$19.34	6.231%	$20.5451	$20.55	$20.55	$20.50
Purchase #5	$127.88	4.873%	$134.1116	$134.11	$134.10	$134.10
Purchase #6	$59.52	5.685%	$62.9037	$62.90	$62.90	$62.90
Purchase #7	$106.26	4.626%	$111.1756	$111.18	$111.20	$111.20
7 purchase totals =	$962.34		$1,025.9032	$1,025.90	$1,025.85	$1,025.90