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	$119.27	7.562%	$128.2892	$128.29	$128.30	$128.30
Purchase #2	$139.65	13.464%	$158.4525	$158.45	$158.45	$158.50
Purchase #3	$89.82	9.391%	$98.255	$98.26	$98.25	$98.30
Purchase #4	$200.74	6.155%	$213.0955	$213.10	$213.10	$213.10
Purchase #5	$56.86	9.646%	$62.3447	$62.34	$62.35	$62.30
Purchase #6	$185.67	11.118%	$206.3128	$206.31	$206.30	$206.30
Purchase #7	$148.91	4.142%	$155.0779	$155.08	$155.10	$155.10
7 purchase totals =	$940.92		$1,021.8276	$1,021.83	$1,021.85	$1,021.90