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	$117.85	8.538%	$127.912	$127.91	$127.90	$127.90
Purchase #2	$103.31	9.301%	$112.9189	$112.92	$112.90	$112.90
Purchase #3	$206.82	6.704%	$220.6852	$220.69	$220.70	$220.70
Purchase #4	$247.71	7.801%	$267.0339	$267.03	$267.05	$267.00
Purchase #5	$19.53	11.447%	$21.7656	$21.77	$21.75	$21.80
Purchase #6	$101.96	9.680%	$111.8297	$111.83	$111.85	$111.80
Purchase #7	$54.36	11.107%	$60.3978	$60.40	$60.40	$60.40
7 purchase totals =	$851.54		$922.5431	$922.55	$922.55	$922.50