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	$193.81	11.105%	$215.3326	$215.33	$215.35	$215.30
Purchase #2	$227.73	6.226%	$241.9085	$241.91	$241.90	$241.90
Purchase #3	$184.26	3.418%	$190.558	$190.56	$190.55	$190.60
Purchase #4	$100.74	11.452%	$112.2767	$112.28	$112.30	$112.30
Purchase #5	$189.32	3.821%	$196.5539	$196.55	$196.55	$196.60
Purchase #6	$70.98	12.381%	$79.768	$79.77	$79.75	$79.80
Purchase #7	$192.67	4.761%	$201.843	$201.84	$201.85	$201.80
7 purchase totals =	$1,159.51		$1,238.2407	$1,238.24	$1,238.25	$1,238.30