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	$81.51	13.513%	$92.5244	$92.52	$92.50	$92.50
Purchase #2	$26.96	9.550%	$29.5347	$29.53	$29.55	$29.50
Purchase #3	$91.29	11.117%	$101.4387	$101.44	$101.45	$101.40
Purchase #4	$77.31	6.536%	$82.363	$82.36	$82.35	$82.40
Purchase #5	$183.37	7.165%	$196.5085	$196.51	$196.50	$196.50
Purchase #6	$169.35	3.558%	$175.3755	$175.38	$175.40	$175.40
Purchase #7	$125.36	13.666%	$142.4917	$142.49	$142.50	$142.50
7 purchase totals =	$755.15		$820.2365	$820.23	$820.25	$820.20