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	$85.53	6.104%	$90.7508	$90.75	$90.75	$90.80
Purchase #2	$115.55	11.251%	$128.5505	$128.55	$128.55	$128.60
Purchase #3	$87.89	6.400%	$93.515	$93.52	$93.50	$93.50
Purchase #4	$162.90	7.695%	$175.4352	$175.44	$175.45	$175.40
Purchase #5	$240.53	5.606%	$254.0141	$254.01	$254.00	$254.00
Purchase #6	$169.42	9.808%	$186.0367	$186.04	$186.05	$186.00
Purchase #7	$92.92	13.294%	$105.2728	$105.27	$105.25	$105.30
7 purchase totals =	$954.74		$1,033.5751	$1,033.58	$1,033.55	$1,033.60