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	$223.83	4.836%	$234.6544	$234.65	$234.65	$234.70
Purchase #2	$56.40	9.741%	$61.8939	$61.89	$61.90	$61.90
Purchase #3	$33.74	7.693%	$36.3356	$36.34	$36.35	$36.30
Purchase #4	$104.69	3.804%	$108.6724	$108.67	$108.65	$108.70
Purchase #5	$174.56	5.572%	$184.2865	$184.29	$184.30	$184.30
Purchase #6	$168.33	11.577%	$187.8176	$187.82	$187.80	$187.80
Purchase #7	$139.41	3.635%	$144.4776	$144.48	$144.50	$144.50
7 purchase totals =	$900.96		$958.1380	$958.14	$958.15	$958.20