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	$127.28	7.850%	$137.2715	$137.27	$137.25	$137.30
Purchase #2	$10.84	3.847%	$11.257	$11.26	$11.25	$11.30
Purchase #3	$174.61	4.755%	$182.9127	$182.91	$182.90	$182.90
Purchase #4	$170.48	3.112%	$175.7853	$175.79	$175.80	$175.80
Purchase #5	$225.26	11.171%	$250.4238	$250.42	$250.40	$250.40
Purchase #6	$83.69	8.657%	$90.935	$90.94	$90.95	$90.90
Purchase #7	$222.90	3.180%	$229.9882	$229.99	$230.00	$230.00
7 purchase totals =	$1,015.06		$1,078.5735	$1,078.58	$1,078.55	$1,078.60