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	$189.59	3.765%	$196.7281	$196.73	$196.75	$196.70
Purchase #2	$234.64	10.630%	$259.5822	$259.58	$259.60	$259.60
Purchase #3	$36.35	13.578%	$41.2856	$41.29	$41.30	$41.30
Purchase #4	$244.35	13.215%	$276.6409	$276.64	$276.65	$276.60
Purchase #5	$68.26	13.165%	$77.2464	$77.25	$77.25	$77.20
Purchase #6	$56.57	4.802%	$59.2865	$59.29	$59.30	$59.30
Purchase #7	$214.68	10.391%	$236.9874	$236.99	$237.00	$237.00
7 purchase totals =	$1,044.44		$1,147.7571	$1,147.77	$1,147.85	$1,147.70