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	$72.27	7.121%	$77.4163	$77.42	$77.40	$77.40
Purchase #2	$161.46	6.502%	$171.9581	$171.96	$171.95	$172.00
Purchase #3	$38.60	12.205%	$43.3111	$43.31	$43.30	$43.30
Purchase #4	$85.82	6.820%	$91.6729	$91.67	$91.65	$91.70
Purchase #5	$53.37	13.487%	$60.568	$60.57	$60.55	$60.60
Purchase #6	$61.74	6.424%	$65.7062	$65.71	$65.70	$65.70
Purchase #7	$100.81	3.311%	$104.1478	$104.15	$104.15	$104.10
7 purchase totals =	$574.07		$614.7804	$614.79	$614.70	$614.80