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	$169.78	11.367%	$189.0789	$189.08	$189.10	$189.10
Purchase #2	$95.42	10.371%	$105.316	$105.32	$105.30	$105.30
Purchase #3	$124.66	3.698%	$129.2699	$129.27	$129.25	$129.30
Purchase #4	$140.30	8.742%	$152.565	$152.57	$152.55	$152.60
Purchase #5	$141.91	3.650%	$147.0897	$147.09	$147.10	$147.10
Purchase #6	$174.44	3.803%	$181.074	$181.07	$181.05	$181.10
Purchase #7	$162.76	11.436%	$181.3732	$181.37	$181.35	$181.40
7 purchase totals =	$1,009.27		$1,085.7667	$1,085.77	$1,085.70	$1,085.90