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	$176.91	8.226%	$191.4626	$191.46	$191.45	$191.50
Purchase #2	$196.59	8.512%	$213.3237	$213.32	$213.30	$213.30
Purchase #3	$77.88	6.692%	$83.0917	$83.09	$83.10	$83.10
Purchase #4	$19.78	12.627%	$22.2776	$22.28	$22.30	$22.30
Purchase #5	$223.34	9.502%	$244.5618	$244.56	$244.55	$244.60
Purchase #6	$245.57	5.803%	$259.8204	$259.82	$259.80	$259.80
Purchase #7	$25.74	8.228%	$27.8579	$27.86	$27.85	$27.90
7 purchase totals =	$965.81		$1,042.3957	$1,042.39	$1,042.35	$1,042.50