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	$172.78	7.275%	$185.3497	$185.35	$185.35	$185.30
Purchase #2	$202.61	4.649%	$212.0293	$212.03	$212.05	$212.00
Purchase #3	$42.85	6.311%	$45.5543	$45.55	$45.55	$45.60
Purchase #4	$142.58	5.646%	$150.6301	$150.63	$150.65	$150.60
Purchase #5	$139.52	10.497%	$154.1654	$154.17	$154.15	$154.20
Purchase #6	$35.89	4.229%	$37.4078	$37.41	$37.40	$37.40
Purchase #7	$207.78	9.582%	$227.6895	$227.69	$227.70	$227.70
7 purchase totals =	$944.01		$1,012.8261	$1,012.83	$1,012.85	$1,012.80