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	$210.85	7.145%	$225.9152	$225.92	$225.90	$225.90
Purchase #2	$109.27	10.641%	$120.8974	$120.90	$120.90	$120.90
Purchase #3	$100.72	5.136%	$105.893	$105.89	$105.90	$105.90
Purchase #4	$33.28	9.608%	$36.4775	$36.48	$36.50	$36.50
Purchase #5	$188.66	12.561%	$212.3576	$212.36	$212.35	$212.40
Purchase #6	$102.67	8.217%	$111.1064	$111.11	$111.10	$111.10
Purchase #7	$186.82	12.796%	$210.7255	$210.73	$210.75	$210.70
7 purchase totals =	$932.27		$1,023.3726	$1,023.39	$1,023.40	$1,023.40