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	$101.93	7.239%	$109.3087	$109.31	$109.30	$109.30
Purchase #2	$115.82	7.586%	$124.6061	$124.61	$124.60	$124.60
Purchase #3	$58.81	4.116%	$61.2306	$61.23	$61.25	$61.20
Purchase #4	$69.30	5.198%	$72.9022	$72.90	$72.90	$72.90
Purchase #5	$231.40	7.842%	$249.5464	$249.55	$249.55	$249.50
Purchase #6	$90.40	6.388%	$96.1748	$96.17	$96.15	$96.20
Purchase #7	$166.54	4.670%	$174.3174	$174.32	$174.30	$174.30
7 purchase totals =	$834.20		$888.0862	$888.09	$888.05	$888.00