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	$158.72	10.199%	$174.9079	$174.91	$174.90	$174.90
Purchase #2	$55.47	9.538%	$60.7607	$60.76	$60.75	$60.80
Purchase #3	$138.27	7.189%	$148.2102	$148.21	$148.20	$148.20
Purchase #4	$103.48	8.784%	$112.5697	$112.57	$112.55	$112.60
Purchase #5	$124.59	11.324%	$138.6986	$138.70	$138.70	$138.70
Purchase #6	$133.73	6.719%	$142.7153	$142.72	$142.70	$142.70
Purchase #7	$55.44	7.362%	$59.5215	$59.52	$59.50	$59.50
7 purchase totals =	$769.70		$837.3839	$837.39	$837.30	$837.40