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	$159.92	9.632%	$175.3235	$175.32	$175.30	$175.30
Purchase #2	$94.98	5.275%	$99.9902	$99.99	$100.00	$100.00
Purchase #3	$42.56	3.220%	$43.9304	$43.93	$43.95	$43.90
Purchase #4	$54.89	13.602%	$62.3561	$62.36	$62.35	$62.40
Purchase #5	$158.81	10.849%	$176.0393	$176.04	$176.05	$176.00
Purchase #6	$137.72	4.636%	$144.1047	$144.10	$144.10	$144.10
Purchase #7	$143.77	10.635%	$159.0599	$159.06	$159.05	$159.10
7 purchase totals =	$792.65		$860.8041	$860.80	$860.80	$860.80