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	$194.56	4.645%	$203.5973	$203.60	$203.60	$203.60
Purchase #2	$97.95	11.465%	$109.18	$109.18	$109.20	$109.20
Purchase #3	$74.94	11.440%	$83.5131	$83.51	$83.50	$83.50
Purchase #4	$112.43	6.669%	$119.928	$119.93	$119.95	$119.90
Purchase #5	$32.80	8.818%	$35.6923	$35.69	$35.70	$35.70
Purchase #6	$142.54	4.764%	$149.3306	$149.33	$149.35	$149.30
Purchase #7	$145.62	3.206%	$150.2886	$150.29	$150.30	$150.30
7 purchase totals =	$800.84		$851.5299	$851.53	$851.60	$851.50