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	$162.58	5.863%	$172.1121	$172.11	$172.10	$172.10
Purchase #2	$99.81	13.760%	$113.5439	$113.54	$113.55	$113.50
Purchase #3	$147.63	5.523%	$155.7836	$155.78	$155.80	$155.80
Purchase #4	$61.82	3.593%	$64.0412	$64.04	$64.05	$64.00
Purchase #5	$190.91	4.108%	$198.7526	$198.75	$198.75	$198.80
Purchase #6	$82.99	7.784%	$89.4499	$89.45	$89.45	$89.40
Purchase #7	$106.44	13.305%	$120.6018	$120.60	$120.60	$120.60
7 purchase totals =	$852.18		$914.2851	$914.27	$914.30	$914.20