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	$80.72	5.712%	$85.3307	$85.33	$85.35	$85.30
Purchase #2	$101.38	12.729%	$114.2847	$114.28	$114.30	$114.30
Purchase #3	$166.29	13.399%	$188.5712	$188.57	$188.55	$188.60
Purchase #4	$89.61	5.636%	$94.6604	$94.66	$94.65	$94.70
Purchase #5	$11.69	3.859%	$12.1411	$12.14	$12.15	$12.10
Purchase #6	$19.89	10.764%	$22.031	$22.03	$22.05	$22.00
Purchase #7	$210.86	3.486%	$218.2106	$218.21	$218.20	$218.20
7 purchase totals =	$680.44		$735.2297	$735.22	$735.25	$735.20