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	$140.49	5.306%	$147.9444	$147.94	$147.95	$147.90
Purchase #2	$153.51	7.124%	$164.4461	$164.45	$164.45	$164.40
Purchase #3	$108.32	6.643%	$115.5157	$115.52	$115.50	$115.50
Purchase #4	$111.80	7.302%	$119.9636	$119.96	$119.95	$120.00
Purchase #5	$220.67	13.505%	$250.4715	$250.47	$250.45	$250.50
Purchase #6	$227.72	5.780%	$240.8822	$240.88	$240.90	$240.90
Purchase #7	$31.72	10.691%	$35.1112	$35.11	$35.10	$35.10
7 purchase totals =	$994.23		$1,074.3347	$1,074.33	$1,074.30	$1,074.30