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	$189.89	7.247%	$203.6513	$203.65	$203.65	$203.70
Purchase #2	$246.73	7.532%	$265.3137	$265.31	$265.30	$265.30
Purchase #3	$114.59	7.632%	$123.3355	$123.34	$123.35	$123.30
Purchase #4	$35.66	3.862%	$37.0372	$37.04	$37.05	$37.00
Purchase #5	$79.49	13.107%	$89.9088	$89.91	$89.90	$89.90
Purchase #6	$30.61	12.683%	$34.4923	$34.49	$34.50	$34.50
Purchase #7	$232.94	3.304%	$240.6363	$240.64	$240.65	$240.60
7 purchase totals =	$929.91		$994.3751	$994.38	$994.40	$994.30