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	$106.97	10.526%	$118.2297	$118.23	$118.25	$118.20
Purchase #2	$211.90	7.658%	$228.1273	$228.13	$228.15	$228.10
Purchase #3	$194.64	5.392%	$205.135	$205.14	$205.15	$205.10
Purchase #4	$122.47	12.442%	$137.7077	$137.71	$137.70	$137.70
Purchase #5	$115.73	10.726%	$128.1432	$128.14	$128.15	$128.10
Purchase #6	$210.64	5.121%	$221.4269	$221.43	$221.45	$221.40
Purchase #7	$105.86	6.375%	$112.6086	$112.61	$112.60	$112.60
7 purchase totals =	$1,068.21		$1,151.3784	$1,151.39	$1,151.45	$1,151.20