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	$177.66	12.292%	$199.498	$199.50	$199.50	$199.50
Purchase #2	$91.89	10.463%	$101.5045	$101.50	$101.50	$101.50
Purchase #3	$220.51	3.755%	$228.7902	$228.79	$228.80	$228.80
Purchase #4	$52.80	11.816%	$59.0388	$59.04	$59.05	$59.00
Purchase #5	$25.80	3.807%	$26.7822	$26.78	$26.80	$26.80
Purchase #6	$98.76	13.811%	$112.3997	$112.40	$112.40	$112.40
Purchase #7	$209.89	11.445%	$233.9119	$233.91	$233.90	$233.90
7 purchase totals =	$877.31		$961.9253	$961.92	$961.95	$961.90