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	$33.78	4.352%	$35.2501	$35.25	$35.25	$35.30
Purchase #2	$137.52	10.411%	$151.8372	$151.84	$151.85	$151.80
Purchase #3	$96.53	4.362%	$100.7406	$100.74	$100.75	$100.70
Purchase #4	$72.62	11.108%	$80.6866	$80.69	$80.70	$80.70
Purchase #5	$250.27	8.497%	$271.5354	$271.54	$271.55	$271.50
Purchase #6	$209.74	4.742%	$219.6859	$219.69	$219.70	$219.70
Purchase #7	$34.95	4.362%	$36.4745	$36.47	$36.45	$36.50
7 purchase totals =	$835.41		$896.2103	$896.22	$896.25	$896.20