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	$195.83	7.192%	$209.9141	$209.91	$209.90	$209.90
Purchase #2	$76.69	7.525%	$82.4609	$82.46	$82.45	$82.50
Purchase #3	$160.85	6.826%	$171.8296	$171.83	$171.85	$171.80
Purchase #4	$45.82	8.103%	$49.5328	$49.53	$49.55	$49.50
Purchase #5	$63.96	5.178%	$67.2718	$67.27	$67.25	$67.30
Purchase #6	$148.91	10.260%	$164.1882	$164.19	$164.20	$164.20
Purchase #7	$42.53	11.821%	$47.5575	$47.56	$47.55	$47.60
7 purchase totals =	$734.59		$792.7549	$792.75	$792.75	$792.80