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	$100.68	12.698%	$113.4643	$113.46	$113.45	$113.50
Purchase #2	$122.51	9.820%	$134.5405	$134.54	$134.55	$134.50
Purchase #3	$104.99	5.490%	$110.754	$110.75	$110.75	$110.80
Purchase #4	$37.55	7.687%	$40.4365	$40.44	$40.45	$40.40
Purchase #5	$86.51	13.683%	$98.3472	$98.35	$98.35	$98.30
Purchase #6	$82.48	8.586%	$89.5617	$89.56	$89.55	$89.60
Purchase #7	$96.98	12.424%	$109.0288	$109.03	$109.05	$109.00
7 purchase totals =	$631.70		$696.1330	$696.13	$696.15	$696.10