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	$182.51	9.773%	$200.3467	$200.35	$200.35	$200.30
Purchase #2	$118.33	8.103%	$127.9183	$127.92	$127.90	$127.90
Purchase #3	$96.79	9.250%	$105.7431	$105.74	$105.75	$105.70
Purchase #4	$212.78	12.518%	$239.4158	$239.42	$239.40	$239.40
Purchase #5	$63.35	9.115%	$69.1244	$69.12	$69.10	$69.10
Purchase #6	$231.79	8.230%	$250.8663	$250.87	$250.85	$250.90
Purchase #7	$26.73	8.290%	$28.9459	$28.95	$28.95	$28.90
7 purchase totals =	$932.28		$1,022.3605	$1,022.37	$1,022.30	$1,022.20