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	11.458%	$189.2334	$189.23	$189.25	$189.20
Purchase #2	$122.37	9.831%	$134.4002	$134.40	$134.40	$134.40
Purchase #3	$221.95	12.587%	$249.8868	$249.89	$249.90	$249.90
Purchase #4	$46.56	9.112%	$50.8025	$50.80	$50.80	$50.80
Purchase #5	$161.49	6.729%	$172.3567	$172.36	$172.35	$172.40
Purchase #6	$182.45	9.842%	$200.4067	$200.41	$200.40	$200.40
Purchase #7	$181.50	9.790%	$199.2689	$199.27	$199.25	$199.30
7 purchase totals =	$1,086.10		$1,196.3552	$1,196.36	$1,196.35	$1,196.40