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	$102.39	7.288%	$109.8522	$109.85	$109.85	$109.90
Purchase #2	$212.43	5.127%	$223.3213	$223.32	$223.30	$223.30
Purchase #3	$97.68	5.234%	$102.7926	$102.79	$102.80	$102.80
Purchase #4	$229.85	4.647%	$240.5311	$240.53	$240.55	$240.50
Purchase #5	$65.73	8.863%	$71.5556	$71.56	$71.55	$71.60
Purchase #6	$233.82	13.278%	$264.8666	$264.87	$264.85	$264.90
Purchase #7	$96.47	12.242%	$108.2799	$108.28	$108.30	$108.30
7 purchase totals =	$1,038.37		$1,121.1993	$1,121.20	$1,121.20	$1,121.30