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	$165.85	9.426%	$181.483	$181.48	$181.50	$181.50
Purchase #2	$133.31	13.107%	$150.7829	$150.78	$150.80	$150.80
Purchase #3	$227.93	8.599%	$247.5297	$247.53	$247.55	$247.50
Purchase #4	$72.69	13.561%	$82.5475	$82.55	$82.55	$82.50
Purchase #5	$89.74	11.305%	$99.8851	$99.89	$99.90	$99.90
Purchase #6	$153.91	3.297%	$158.9844	$158.98	$159.00	$159.00
Purchase #7	$80.75	9.701%	$88.5836	$88.58	$88.60	$88.60
7 purchase totals =	$924.18		$1,009.7962	$1,009.79	$1,009.90	$1,009.80