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	$191.41	6.302%	$203.4727	$203.47	$203.45	$203.50
Purchase #2	$81.56	6.593%	$86.9373	$86.94	$86.95	$86.90
Purchase #3	$99.62	11.269%	$110.8462	$110.85	$110.85	$110.80
Purchase #4	$188.84	4.655%	$197.6305	$197.63	$197.65	$197.60
Purchase #5	$161.71	11.505%	$180.3147	$180.31	$180.30	$180.30
Purchase #6	$71.96	9.615%	$78.879	$78.88	$78.90	$78.90
Purchase #7	$202.58	10.323%	$223.4923	$223.49	$223.50	$223.50
7 purchase totals =	$997.68		$1,081.5727	$1,081.57	$1,081.60	$1,081.50