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	$172.33	10.454%	$190.3454	$190.35	$190.35	$190.30
Purchase #2	$67.71	7.415%	$72.7307	$72.73	$72.75	$72.70
Purchase #3	$91.39	9.254%	$99.8472	$99.85	$99.85	$99.80
Purchase #4	$202.28	11.321%	$225.1801	$225.18	$225.20	$225.20
Purchase #5	$6.44	9.640%	$7.0608	$7.06	$7.05	$7.10
Purchase #6	$52.66	8.858%	$57.3246	$57.32	$57.30	$57.30
Purchase #7	$170.33	5.455%	$179.6215	$179.62	$179.60	$179.60
7 purchase totals =	$763.14		$832.1103	$832.11	$832.10	$832.00