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	$79.50	7.194%	$85.2192	$85.22	$85.20	$85.20
Purchase #2	$77.76	3.116%	$80.183	$80.18	$80.20	$80.20
Purchase #3	$224.69	10.162%	$247.523	$247.52	$247.50	$247.50
Purchase #4	$104.86	10.323%	$115.6847	$115.68	$115.70	$115.70
Purchase #5	$154.93	4.762%	$162.3078	$162.31	$162.30	$162.30
Purchase #6	$115.91	13.784%	$131.887	$131.89	$131.90	$131.90
Purchase #7	$239.79	10.490%	$264.944	$264.94	$264.95	$264.90
7 purchase totals =	$997.44		$1,087.7487	$1,087.74	$1,087.75	$1,087.70