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	$166.79	11.137%	$185.3654	$185.37	$185.35	$185.40
Purchase #2	$19.32	5.728%	$20.4266	$20.43	$20.45	$20.40
Purchase #3	$79.96	4.715%	$83.7301	$83.73	$83.75	$83.70
Purchase #4	$212.57	8.114%	$229.8179	$229.82	$229.80	$229.80
Purchase #5	$198.76	9.109%	$216.865	$216.87	$216.85	$216.90
Purchase #6	$90.47	7.856%	$97.5773	$97.58	$97.60	$97.60
Purchase #7	$49.25	6.136%	$52.272	$52.27	$52.25	$52.30
7 purchase totals =	$817.12		$886.0543	$886.07	$886.05	$886.10