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	$191.91	8.114%	$207.4816	$207.48	$207.50	$207.50
Purchase #2	$52.54	6.142%	$55.767	$55.77	$55.75	$55.80
Purchase #3	$179.59	5.380%	$189.2519	$189.25	$189.25	$189.30
Purchase #4	$211.94	11.499%	$236.311	$236.31	$236.30	$236.30
Purchase #5	$112.59	7.327%	$120.8395	$120.84	$120.85	$120.80
Purchase #6	$209.49	10.488%	$231.4613	$231.46	$231.45	$231.50
Purchase #7	$103.43	5.638%	$109.2614	$109.26	$109.25	$109.30
7 purchase totals =	$1,061.49		$1,150.3737	$1,150.37	$1,150.35	$1,150.50