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	$185.83	3.285%	$191.9345	$191.93	$191.95	$191.90
Purchase #2	$172.66	4.695%	$180.7664	$180.77	$180.75	$180.80
Purchase #3	$147.40	3.405%	$152.419	$152.42	$152.40	$152.40
Purchase #4	$212.41	9.792%	$233.2092	$233.21	$233.20	$233.20
Purchase #5	$17.66	10.154%	$19.4532	$19.45	$19.45	$19.50
Purchase #6	$66.77	8.192%	$72.2398	$72.24	$72.25	$72.20
Purchase #7	$248.39	8.649%	$269.8733	$269.87	$269.85	$269.90
7 purchase totals =	$1,051.12		$1,119.8954	$1,119.89	$1,119.85	$1,119.90