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	$205.29	4.369%	$214.2591	$214.26	$214.25	$214.30
Purchase #2	$101.84	8.869%	$110.8722	$110.87	$110.85	$110.90
Purchase #3	$174.92	12.194%	$196.2497	$196.25	$196.25	$196.20
Purchase #4	$139.79	7.521%	$150.3036	$150.30	$150.30	$150.30
Purchase #5	$105.78	4.674%	$110.7242	$110.72	$110.70	$110.70
Purchase #6	$66.82	3.496%	$69.156	$69.16	$69.15	$69.20
Purchase #7	$156.84	5.373%	$165.267	$165.27	$165.25	$165.30
7 purchase totals =	$951.28		$1,016.8318	$1,016.83	$1,016.75	$1,016.90