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	$29.33	10.773%	$32.4897	$32.49	$32.50	$32.50
Purchase #2	$82.63	12.389%	$92.867	$92.87	$92.85	$92.90
Purchase #3	$133.49	9.750%	$146.5053	$146.51	$146.50	$146.50
Purchase #4	$204.46	9.362%	$223.6015	$223.60	$223.60	$223.60
Purchase #5	$181.51	4.273%	$189.2659	$189.27	$189.25	$189.30
Purchase #6	$82.59	4.688%	$86.4618	$86.46	$86.45	$86.50
Purchase #7	$50.50	11.199%	$56.1555	$56.16	$56.15	$56.20
7 purchase totals =	$764.51		$827.3467	$827.36	$827.30	$827.50