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	$87.46	10.356%	$96.5174	$96.52	$96.50	$96.50
Purchase #2	$58.45	8.834%	$63.6135	$63.61	$63.60	$63.60
Purchase #3	$38.61	7.584%	$41.5382	$41.54	$41.55	$41.50
Purchase #4	$72.98	6.771%	$77.9215	$77.92	$77.90	$77.90
Purchase #5	$102.29	8.725%	$111.2148	$111.21	$111.20	$111.20
Purchase #6	$149.41	10.735%	$165.4492	$165.45	$165.45	$165.40
Purchase #7	$76.65	4.814%	$80.3399	$80.34	$80.35	$80.30
7 purchase totals =	$585.85		$636.5945	$636.59	$636.55	$636.40