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	$108.59	13.682%	$123.4473	$123.45	$123.45	$123.40
Purchase #2	$75.98	9.448%	$83.1586	$83.16	$83.15	$83.20
Purchase #3	$62.28	3.154%	$64.2443	$64.24	$64.25	$64.20
Purchase #4	$139.54	4.704%	$146.104	$146.10	$146.10	$146.10
Purchase #5	$60.60	7.562%	$65.1826	$65.18	$65.20	$65.20
Purchase #6	$98.73	6.624%	$105.2699	$105.27	$105.25	$105.30
Purchase #7	$157.64	4.225%	$164.3003	$164.30	$164.30	$164.30
7 purchase totals =	$703.36		$751.7070	$751.70	$751.70	$751.70