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	$223.84	5.535%	$236.2295	$236.23	$236.25	$236.20
Purchase #2	$209.75	10.753%	$232.3044	$232.30	$232.30	$232.30
Purchase #3	$92.86	13.584%	$105.4741	$105.47	$105.45	$105.50
Purchase #4	$87.76	13.279%	$99.4137	$99.41	$99.40	$99.40
Purchase #5	$205.39	6.790%	$219.336	$219.34	$219.35	$219.30
Purchase #6	$226.61	7.185%	$242.8919	$242.89	$242.90	$242.90
Purchase #7	$250.52	5.271%	$263.7249	$263.72	$263.70	$263.70
7 purchase totals =	$1,296.73		$1,399.3745	$1,399.36	$1,399.35	$1,399.30