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	$159.62	4.582%	$166.9338	$166.93	$166.95	$166.90
Purchase #2	$242.55	8.482%	$263.1231	$263.12	$263.10	$263.10
Purchase #3	$80.46	12.249%	$90.3155	$90.32	$90.30	$90.30
Purchase #4	$102.32	3.354%	$105.7518	$105.75	$105.75	$105.80
Purchase #5	$185.62	7.361%	$199.2835	$199.28	$199.30	$199.30
Purchase #6	$152.99	9.472%	$167.4812	$167.48	$167.50	$167.50
Purchase #7	$208.41	3.294%	$215.275	$215.28	$215.30	$215.30
7 purchase totals =	$1,131.97		$1,208.1639	$1,208.16	$1,208.20	$1,208.20