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	$86.38	7.124%	$92.5337	$92.53	$92.55	$92.50
Purchase #2	$134.95	11.279%	$150.171	$150.17	$150.15	$150.20
Purchase #3	$13.84	4.542%	$14.4686	$14.47	$14.45	$14.50
Purchase #4	$250.37	7.592%	$269.3781	$269.38	$269.40	$269.40
Purchase #5	$42.68	12.229%	$47.8993	$47.90	$47.90	$47.90
Purchase #6	$42.50	11.606%	$47.4326	$47.43	$47.45	$47.40
Purchase #7	$247.57	4.466%	$258.6265	$258.63	$258.65	$258.60
7 purchase totals =	$818.29		$880.5098	$880.51	$880.55	$880.50