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	$222.64	12.404%	$250.2563	$250.26	$250.25	$250.30
Purchase #2	$23.43	10.408%	$25.8686	$25.87	$25.85	$25.90
Purchase #3	$225.93	12.118%	$253.3082	$253.31	$253.30	$253.30
Purchase #4	$19.61	11.716%	$21.9075	$21.91	$21.90	$21.90
Purchase #5	$227.86	9.663%	$249.8781	$249.88	$249.90	$249.90
Purchase #6	$45.59	9.782%	$50.0496	$50.05	$50.05	$50.00
Purchase #7	$69.63	11.506%	$77.6416	$77.64	$77.65	$77.60
7 purchase totals =	$834.69		$928.9099	$928.92	$928.90	$928.90