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	$168.90	12.854%	$190.6104	$190.61	$190.60	$190.60
Purchase #2	$147.89	7.639%	$159.1873	$159.19	$159.20	$159.20
Purchase #3	$39.52	4.661%	$41.362	$41.36	$41.35	$41.40
Purchase #4	$250.52	7.530%	$269.3842	$269.38	$269.40	$269.40
Purchase #5	$38.74	12.612%	$43.6259	$43.63	$43.65	$43.60
Purchase #6	$185.55	4.234%	$193.4062	$193.41	$193.40	$193.40
Purchase #7	$182.60	9.838%	$200.5642	$200.56	$200.55	$200.60
7 purchase totals =	$1,013.72		$1,098.1402	$1,098.14	$1,098.15	$1,098.20