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	$126.96	12.621%	$142.9836	$142.98	$143.00	$143.00
Purchase #2	$50.90	5.803%	$53.8537	$53.85	$53.85	$53.90
Purchase #3	$33.90	4.281%	$35.3513	$35.35	$35.35	$35.40
Purchase #4	$89.56	4.390%	$93.4917	$93.49	$93.50	$93.50
Purchase #5	$64.79	10.119%	$71.3461	$71.35	$71.35	$71.30
Purchase #6	$145.87	4.746%	$152.793	$152.79	$152.80	$152.80
Purchase #7	$110.72	7.472%	$118.993	$118.99	$119.00	$119.00
7 purchase totals =	$622.70		$668.8124	$668.80	$668.85	$668.90