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	$234.38	5.435%	$247.1186	$247.12	$247.10	$247.10
Purchase #2	$95.89	9.809%	$105.2959	$105.30	$105.30	$105.30
Purchase #3	$65.78	10.188%	$72.4817	$72.48	$72.50	$72.50
Purchase #4	$78.87	4.633%	$82.524	$82.52	$82.50	$82.50
Purchase #5	$168.51	8.328%	$182.5435	$182.54	$182.55	$182.50
Purchase #6	$165.81	9.597%	$181.7228	$181.72	$181.70	$181.70
Purchase #7	$64.57	13.759%	$73.4542	$73.45	$73.45	$73.50
7 purchase totals =	$873.81		$945.1407	$945.13	$945.10	$945.10