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	$96.45	5.778%	$102.0229	$102.02	$102.00	$102.00
Purchase #2	$40.34	5.474%	$42.5482	$42.55	$42.55	$42.50
Purchase #3	$168.88	6.347%	$179.5988	$179.60	$179.60	$179.60
Purchase #4	$71.74	13.821%	$81.6552	$81.66	$81.65	$81.70
Purchase #5	$88.96	10.698%	$98.4769	$98.48	$98.50	$98.50
Purchase #6	$215.73	10.567%	$238.5262	$238.53	$238.55	$238.50
Purchase #7	$229.40	5.736%	$242.5584	$242.56	$242.55	$242.60
7 purchase totals =	$911.50		$985.3866	$985.40	$985.40	$985.40