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	$41.88	8.274%	$45.3452	$45.35	$45.35	$45.30
Purchase #2	$103.88	6.371%	$110.4982	$110.50	$110.50	$110.50
Purchase #3	$89.66	12.768%	$101.1078	$101.11	$101.10	$101.10
Purchase #4	$68.57	4.511%	$71.6632	$71.66	$71.65	$71.70
Purchase #5	$182.43	13.227%	$206.56	$206.56	$206.55	$206.60
Purchase #6	$169.50	11.106%	$188.3247	$188.32	$188.30	$188.30
Purchase #7	$160.25	7.257%	$171.8793	$171.88	$171.90	$171.90
7 purchase totals =	$816.17		$895.3784	$895.38	$895.35	$895.40