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	$146.37	4.315%	$152.6859	$152.69	$152.70	$152.70
Purchase #2	$10.50	8.548%	$11.3975	$11.40	$11.40	$11.40
Purchase #3	$72.72	13.863%	$82.8012	$82.80	$82.80	$82.80
Purchase #4	$138.63	10.148%	$152.6982	$152.70	$152.70	$152.70
Purchase #5	$145.97	13.785%	$166.092	$166.09	$166.10	$166.10
Purchase #6	$214.86	11.432%	$239.4228	$239.42	$239.40	$239.40
Purchase #7	$242.88	13.251%	$275.064	$275.06	$275.05	$275.10
7 purchase totals =	$971.93		$1,080.1616	$1,080.16	$1,080.15	$1,080.20