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	$174.53	3.438%	$180.5303	$180.53	$180.55	$180.50
Purchase #2	$221.89	11.795%	$248.0619	$248.06	$248.05	$248.10
Purchase #3	$118.93	5.830%	$125.8636	$125.86	$125.85	$125.90
Purchase #4	$80.54	13.645%	$91.5297	$91.53	$91.55	$91.50
Purchase #5	$174.50	12.334%	$196.0228	$196.02	$196.00	$196.00
Purchase #6	$40.28	9.389%	$44.0619	$44.06	$44.05	$44.10
Purchase #7	$191.80	7.549%	$206.279	$206.28	$206.30	$206.30
7 purchase totals =	$1,002.47		$1,092.3492	$1,092.34	$1,092.35	$1,092.40