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	$172.91	11.428%	$192.6702	$192.67	$192.65	$192.70
Purchase #2	$161.55	6.220%	$171.5984	$171.60	$171.60	$171.60
Purchase #3	$220.73	7.613%	$237.5342	$237.53	$237.55	$237.50
Purchase #4	$97.88	13.681%	$111.271	$111.27	$111.25	$111.30
Purchase #5	$100.88	8.216%	$109.1683	$109.17	$109.15	$109.20
Purchase #6	$60.29	8.185%	$65.2247	$65.22	$65.20	$65.20
Purchase #7	$236.57	13.734%	$269.0605	$269.06	$269.05	$269.10
7 purchase totals =	$1,050.81		$1,156.5273	$1,156.52	$1,156.45	$1,156.60