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	$215.52	3.391%	$222.8283	$222.83	$222.85	$222.80
Purchase #2	$100.58	7.811%	$108.4363	$108.44	$108.45	$108.40
Purchase #3	$19.25	4.736%	$20.1617	$20.16	$20.15	$20.20
Purchase #4	$212.90	4.450%	$222.3741	$222.37	$222.35	$222.40
Purchase #5	$188.82	7.674%	$203.31	$203.31	$203.30	$203.30
Purchase #6	$161.64	13.291%	$183.1236	$183.12	$183.10	$183.10
Purchase #7	$162.53	9.684%	$178.2694	$178.27	$178.25	$178.30
7 purchase totals =	$1,061.24		$1,138.5034	$1,138.50	$1,138.45	$1,138.50