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	$128.76	3.278%	$132.9808	$132.98	$133.00	$133.00
Purchase #2	$220.86	7.168%	$236.6912	$236.69	$236.70	$236.70
Purchase #3	$80.75	6.556%	$86.044	$86.04	$86.05	$86.00
Purchase #4	$90.53	8.580%	$98.2975	$98.30	$98.30	$98.30
Purchase #5	$53.91	13.172%	$61.011	$61.01	$61.00	$61.00
Purchase #6	$34.63	7.728%	$37.3062	$37.31	$37.30	$37.30
Purchase #7	$83.68	8.529%	$90.8171	$90.82	$90.80	$90.80
7 purchase totals =	$693.12		$743.1478	$743.15	$743.15	$743.10