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	$202.39	3.705%	$209.8885	$209.89	$209.90	$209.90
Purchase #2	$96.67	6.662%	$103.1102	$103.11	$103.10	$103.10
Purchase #3	$78.69	13.386%	$89.2234	$89.22	$89.20	$89.20
Purchase #4	$71.31	6.192%	$75.7255	$75.73	$75.75	$75.70
Purchase #5	$87.63	8.869%	$95.4019	$95.40	$95.40	$95.40
Purchase #6	$228.70	6.611%	$243.8194	$243.82	$243.80	$243.80
Purchase #7	$47.96	7.578%	$51.5944	$51.59	$51.60	$51.60
7 purchase totals =	$813.35		$868.7633	$868.76	$868.75	$868.70