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	$161.75	4.571%	$169.1436	$169.14	$169.15	$169.10
Purchase #2	$7.59	4.225%	$7.9107	$7.91	$7.90	$7.90
Purchase #3	$52.34	4.135%	$54.5043	$54.50	$54.50	$54.50
Purchase #4	$233.40	9.222%	$254.9241	$254.92	$254.90	$254.90
Purchase #5	$73.31	7.395%	$78.7313	$78.73	$78.75	$78.70
Purchase #6	$80.25	12.774%	$90.5011	$90.50	$90.50	$90.50
Purchase #7	$119.61	12.379%	$134.4165	$134.42	$134.40	$134.40
7 purchase totals =	$728.25		$790.1316	$790.12	$790.10	$790.00