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	$164.86	9.668%	$180.7987	$180.80	$180.80	$180.80
Purchase #2	$128.70	5.243%	$135.4477	$135.45	$135.45	$135.40
Purchase #3	$78.96	11.652%	$88.1604	$88.16	$88.15	$88.20
Purchase #4	$184.65	6.363%	$196.3993	$196.40	$196.40	$196.40
Purchase #5	$56.73	13.603%	$64.447	$64.45	$64.45	$64.40
Purchase #6	$73.36	7.264%	$78.6889	$78.69	$78.70	$78.70
Purchase #7	$196.72	12.553%	$221.4143	$221.41	$221.40	$221.40
7 purchase totals =	$883.98		$965.3563	$965.36	$965.35	$965.30