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	$96.77	4.280%	$100.9118	$100.91	$100.90	$100.90
Purchase #2	$203.75	3.243%	$210.3576	$210.36	$210.35	$210.40
Purchase #3	$110.84	6.243%	$117.7597	$117.76	$117.75	$117.80
Purchase #4	$211.75	4.866%	$222.0538	$222.05	$222.05	$222.10
Purchase #5	$233.63	4.765%	$244.7625	$244.76	$244.75	$244.80
Purchase #6	$167.51	13.672%	$190.412	$190.41	$190.40	$190.40
Purchase #7	$62.89	7.281%	$67.469	$67.47	$67.45	$67.50
7 purchase totals =	$1,087.14		$1,153.7264	$1,153.72	$1,153.65	$1,153.90