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	$46.61	8.287%	$50.4726	$50.47	$50.45	$50.50
Purchase #2	$196.96	13.449%	$223.4492	$223.45	$223.45	$223.40
Purchase #3	$223.25	13.488%	$253.362	$253.36	$253.35	$253.40
Purchase #4	$20.34	12.258%	$22.8333	$22.83	$22.85	$22.80
Purchase #5	$143.41	6.343%	$152.5065	$152.51	$152.50	$152.50
Purchase #6	$205.94	3.646%	$213.4486	$213.45	$213.45	$213.40
Purchase #7	$96.47	13.369%	$109.3671	$109.37	$109.35	$109.40
7 purchase totals =	$932.98		$1,025.4393	$1,025.44	$1,025.40	$1,025.40