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	$165.59	3.746%	$171.793	$171.79	$171.80	$171.80
Purchase #2	$15.63	12.404%	$17.5687	$17.57	$17.55	$17.60
Purchase #3	$229.65	4.625%	$240.2713	$240.27	$240.25	$240.30
Purchase #4	$170.53	11.225%	$189.672	$189.67	$189.65	$189.70
Purchase #5	$56.63	13.525%	$64.2892	$64.29	$64.30	$64.30
Purchase #6	$181.92	5.470%	$191.871	$191.87	$191.85	$191.90
Purchase #7	$170.83	5.548%	$180.3076	$180.31	$180.30	$180.30
7 purchase totals =	$990.78		$1,055.7728	$1,055.77	$1,055.70	$1,055.90