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	$237.73	13.164%	$269.0248	$269.02	$269.00	$269.00
Purchase #2	$55.55	9.780%	$60.9828	$60.98	$61.00	$61.00
Purchase #3	$171.85	13.492%	$195.036	$195.04	$195.05	$195.00
Purchase #4	$130.45	5.572%	$137.7187	$137.72	$137.70	$137.70
Purchase #5	$84.34	6.155%	$89.5311	$89.53	$89.55	$89.50
Purchase #6	$179.86	10.369%	$198.5097	$198.51	$198.50	$198.50
Purchase #7	$172.36	6.601%	$183.7375	$183.74	$183.75	$183.70
7 purchase totals =	$1,032.14		$1,134.5406	$1,134.54	$1,134.55	$1,134.40