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	$65.73	12.206%	$73.753	$73.75	$73.75	$73.80
Purchase #2	$78.64	4.594%	$82.2527	$82.25	$82.25	$82.30
Purchase #3	$237.53	6.181%	$252.2117	$252.21	$252.20	$252.20
Purchase #4	$194.29	7.813%	$209.4699	$209.47	$209.45	$209.50
Purchase #5	$180.78	4.809%	$189.4737	$189.47	$189.45	$189.50
Purchase #6	$81.76	6.217%	$86.843	$86.84	$86.85	$86.80
Purchase #7	$181.62	8.256%	$196.6145	$196.61	$196.60	$196.60
7 purchase totals =	$1,020.35		$1,090.6185	$1,090.60	$1,090.55	$1,090.70