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	$128.27	11.333%	$142.8068	$142.81	$142.80	$142.80
Purchase #2	$38.43	7.834%	$41.4406	$41.44	$41.45	$41.40
Purchase #3	$197.77	4.279%	$206.2326	$206.23	$206.25	$206.20
Purchase #4	$28.32	10.646%	$31.3349	$31.33	$31.35	$31.30
Purchase #5	$83.73	7.319%	$89.8582	$89.86	$89.85	$89.90
Purchase #6	$33.82	7.691%	$36.4211	$36.42	$36.40	$36.40
Purchase #7	$195.55	9.539%	$214.2035	$214.20	$214.20	$214.20
7 purchase totals =	$705.89		$762.2977	$762.29	$762.30	$762.20