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	$41.36	9.433%	$45.2615	$45.26	$45.25	$45.30
Purchase #2	$166.56	8.228%	$180.2646	$180.26	$180.25	$180.30
Purchase #3	$178.52	3.696%	$185.1181	$185.12	$185.10	$185.10
Purchase #4	$187.54	4.689%	$196.3338	$196.33	$196.35	$196.30
Purchase #5	$227.30	6.413%	$241.8767	$241.88	$241.90	$241.90
Purchase #6	$35.56	5.520%	$37.5229	$37.52	$37.50	$37.50
Purchase #7	$129.98	12.706%	$146.4953	$146.50	$146.50	$146.50
7 purchase totals =	$966.82		$1,032.8729	$1,032.87	$1,032.85	$1,032.90