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	$186.58	9.578%	$204.4506	$204.45	$204.45	$204.50
Purchase #2	$49.38	11.165%	$54.8933	$54.89	$54.90	$54.90
Purchase #3	$171.57	13.141%	$194.116	$194.12	$194.10	$194.10
Purchase #4	$134.64	3.817%	$139.7792	$139.78	$139.80	$139.80
Purchase #5	$166.30	11.749%	$185.8386	$185.84	$185.85	$185.80
Purchase #6	$165.82	12.488%	$186.5276	$186.53	$186.55	$186.50
Purchase #7	$98.82	9.442%	$108.1506	$108.15	$108.15	$108.20
7 purchase totals =	$973.11		$1,073.7559	$1,073.76	$1,073.80	$1,073.80