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	$184.25	8.578%	$200.055	$200.06	$200.05	$200.10
Purchase #2	$152.81	4.115%	$159.0981	$159.10	$159.10	$159.10
Purchase #3	$42.31	7.693%	$45.5649	$45.56	$45.55	$45.60
Purchase #4	$241.47	12.340%	$271.2674	$271.27	$271.25	$271.30
Purchase #5	$23.89	13.668%	$27.1553	$27.16	$27.15	$27.20
Purchase #6	$78.45	8.584%	$85.1841	$85.18	$85.20	$85.20
Purchase #7	$162.34	7.708%	$174.8532	$174.85	$174.85	$174.90
7 purchase totals =	$885.52		$963.1780	$963.18	$963.15	$963.40