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	$195.65	11.518%	$218.185	$218.19	$218.20	$218.20
Purchase #2	$181.39	8.485%	$196.7809	$196.78	$196.80	$196.80
Purchase #3	$82.29	11.557%	$91.8003	$91.80	$91.80	$91.80
Purchase #4	$176.84	6.776%	$188.8227	$188.82	$188.80	$188.80
Purchase #5	$246.83	5.173%	$259.5985	$259.60	$259.60	$259.60
Purchase #6	$245.64	7.686%	$264.5199	$264.52	$264.50	$264.50
Purchase #7	$59.46	8.317%	$64.4053	$64.41	$64.40	$64.40
7 purchase totals =	$1,188.10		$1,284.1126	$1,284.12	$1,284.10	$1,284.10