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	$76.53	6.461%	$81.4746	$81.47	$81.45	$81.50
Purchase #2	$205.86	8.135%	$222.6067	$222.61	$222.60	$222.60
Purchase #3	$46.34	8.740%	$50.3901	$50.39	$50.40	$50.40
Purchase #4	$125.38	6.342%	$133.3316	$133.33	$133.35	$133.30
Purchase #5	$181.78	10.511%	$200.8869	$200.89	$200.90	$200.90
Purchase #6	$185.96	3.723%	$192.8833	$192.88	$192.90	$192.90
Purchase #7	$239.34	11.861%	$267.7281	$267.73	$267.75	$267.70
7 purchase totals =	$1,061.19		$1,149.3013	$1,149.30	$1,149.35	$1,149.30