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	$66.52	7.873%	$71.7571	$71.76	$71.75	$71.80
Purchase #2	$103.84	13.739%	$118.1066	$118.11	$118.10	$118.10
Purchase #3	$142.62	11.134%	$158.4993	$158.50	$158.50	$158.50
Purchase #4	$127.91	12.820%	$144.3081	$144.31	$144.30	$144.30
Purchase #5	$152.70	9.117%	$166.6217	$166.62	$166.60	$166.60
Purchase #6	$82.38	8.357%	$89.2645	$89.26	$89.25	$89.30
Purchase #7	$18.61	6.160%	$19.7564	$19.76	$19.75	$19.80
7 purchase totals =	$694.58		$768.3137	$768.32	$768.25	$768.40