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	$128.54	12.133%	$144.1358	$144.14	$144.15	$144.10
Purchase #2	$140.79	11.156%	$156.4965	$156.50	$156.50	$156.50
Purchase #3	$221.86	7.597%	$238.7147	$238.71	$238.70	$238.70
Purchase #4	$71.94	10.593%	$79.5606	$79.56	$79.55	$79.60
Purchase #5	$183.69	10.814%	$203.5542	$203.55	$203.55	$203.60
Purchase #6	$101.53	8.149%	$109.8037	$109.80	$109.80	$109.80
Purchase #7	$147.81	11.587%	$164.9367	$164.94	$164.95	$164.90
7 purchase totals =	$996.16		$1,097.2022	$1,097.20	$1,097.20	$1,097.20