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	$76.79	7.367%	$82.4471	$82.45	$82.45	$82.40
Purchase #2	$175.98	4.348%	$183.6316	$183.63	$183.65	$183.60
Purchase #3	$77.50	6.116%	$82.2399	$82.24	$82.25	$82.20
Purchase #4	$190.46	13.798%	$216.7397	$216.74	$216.75	$216.70
Purchase #5	$59.95	5.774%	$63.4115	$63.41	$63.40	$63.40
Purchase #6	$160.52	11.740%	$179.365	$179.37	$179.35	$179.40
Purchase #7	$243.53	13.797%	$277.1298	$277.13	$277.15	$277.10
7 purchase totals =	$984.73		$1,084.9646	$1,084.97	$1,085.00	$1,084.80