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	$219.50	11.213%	$244.1125	$244.11	$244.10	$244.10
Purchase #2	$31.97	4.250%	$33.3287	$33.33	$33.35	$33.30
Purchase #3	$10.52	4.400%	$10.9829	$10.98	$11.00	$11.00
Purchase #4	$58.31	6.786%	$62.2669	$62.27	$62.25	$62.30
Purchase #5	$101.91	3.594%	$105.5726	$105.57	$105.55	$105.60
Purchase #6	$44.48	10.479%	$49.1411	$49.14	$49.15	$49.10
Purchase #7	$103.39	5.856%	$109.4445	$109.44	$109.45	$109.40
7 purchase totals =	$570.08		$614.8492	$614.84	$614.85	$614.80