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	$233.45	7.623%	$251.2459	$251.25	$251.25	$251.20
Purchase #2	$148.31	7.532%	$159.4807	$159.48	$159.50	$159.50
Purchase #3	$102.38	11.777%	$114.4373	$114.44	$114.45	$114.40
Purchase #4	$240.69	5.379%	$253.6367	$253.64	$253.65	$253.60
Purchase #5	$38.78	9.583%	$42.4963	$42.50	$42.50	$42.50
Purchase #6	$250.59	5.569%	$264.5454	$264.55	$264.55	$264.50
Purchase #7	$88.56	7.511%	$95.2117	$95.21	$95.20	$95.20
7 purchase totals =	$1,102.76		$1,181.0540	$1,181.07	$1,181.10	$1,180.90