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	$52.82	10.112%	$58.1612	$58.16	$58.15	$58.20
Purchase #2	$159.60	9.343%	$174.5114	$174.51	$174.50	$174.50
Purchase #3	$114.79	7.366%	$123.2454	$123.25	$123.25	$123.20
Purchase #4	$177.37	10.662%	$196.2812	$196.28	$196.30	$196.30
Purchase #5	$246.62	3.327%	$254.825	$254.83	$254.85	$254.80
Purchase #6	$162.33	10.582%	$179.5078	$179.51	$179.50	$179.50
Purchase #7	$209.51	11.261%	$233.1029	$233.10	$233.10	$233.10
7 purchase totals =	$1,123.04		$1,219.6349	$1,219.64	$1,219.65	$1,219.60