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	$213.45	4.625%	$223.3221	$223.32	$223.30	$223.30
Purchase #2	$98.52	5.303%	$103.7445	$103.74	$103.75	$103.70
Purchase #3	$215.32	6.597%	$229.5247	$229.52	$229.50	$229.50
Purchase #4	$249.77	13.603%	$283.7462	$283.75	$283.75	$283.70
Purchase #5	$167.91	4.272%	$175.0831	$175.08	$175.10	$175.10
Purchase #6	$168.32	10.242%	$185.5593	$185.56	$185.55	$185.60
Purchase #7	$81.33	5.311%	$85.6494	$85.65	$85.65	$85.60
7 purchase totals =	$1,194.62		$1,286.6293	$1,286.62	$1,286.60	$1,286.50