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	$230.74	5.686%	$243.8599	$243.86	$243.85	$243.90
Purchase #2	$211.76	8.414%	$229.5775	$229.58	$229.60	$229.60
Purchase #3	$144.60	3.444%	$149.58	$149.58	$149.60	$149.60
Purchase #4	$55.61	7.303%	$59.6712	$59.67	$59.65	$59.70
Purchase #5	$92.59	9.663%	$101.537	$101.54	$101.55	$101.50
Purchase #6	$54.46	11.406%	$60.6717	$60.67	$60.65	$60.70
Purchase #7	$160.37	7.210%	$171.9327	$171.93	$171.95	$171.90
7 purchase totals =	$950.13		$1,016.8300	$1,016.83	$1,016.85	$1,016.90