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	$52.30	4.611%	$54.7116	$54.71	$54.70	$54.70
Purchase #2	$225.39	7.834%	$243.0471	$243.05	$243.05	$243.00
Purchase #3	$209.61	13.491%	$237.8885	$237.89	$237.90	$237.90
Purchase #4	$16.33	12.254%	$18.3311	$18.33	$18.35	$18.30
Purchase #5	$236.61	13.732%	$269.1013	$269.10	$269.10	$269.10
Purchase #6	$72.63	13.428%	$82.3828	$82.38	$82.40	$82.40
Purchase #7	$151.91	5.117%	$159.6832	$159.68	$159.70	$159.70
7 purchase totals =	$964.78		$1,065.1456	$1,065.14	$1,065.20	$1,065.10