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	$152.82	11.321%	$170.1208	$170.12	$170.10	$170.10
Purchase #2	$61.28	5.428%	$64.6063	$64.61	$64.60	$64.60
Purchase #3	$228.80	4.684%	$239.517	$239.52	$239.50	$239.50
Purchase #4	$130.92	11.430%	$145.8842	$145.88	$145.90	$145.90
Purchase #5	$183.48	7.133%	$196.5676	$196.57	$196.55	$196.60
Purchase #6	$128.97	8.801%	$140.3206	$140.32	$140.30	$140.30
Purchase #7	$202.63	9.315%	$221.505	$221.51	$221.50	$221.50
7 purchase totals =	$1,088.90		$1,178.5215	$1,178.53	$1,178.45	$1,178.50