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	$191.28	12.736%	$215.6414	$215.64	$215.65	$215.60
Purchase #2	$144.45	12.309%	$162.2304	$162.23	$162.25	$162.20
Purchase #3	$201.90	11.815%	$225.7545	$225.75	$225.75	$225.80
Purchase #4	$53.45	12.489%	$60.1254	$60.13	$60.15	$60.10
Purchase #5	$186.80	7.162%	$200.1786	$200.18	$200.20	$200.20
Purchase #6	$227.31	10.183%	$250.457	$250.46	$250.45	$250.50
Purchase #7	$155.70	4.315%	$162.4185	$162.42	$162.40	$162.40
7 purchase totals =	$1,160.89		$1,276.8058	$1,276.81	$1,276.85	$1,276.80