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	$98.35	5.398%	$103.6589	$103.66	$103.65	$103.70
Purchase #2	$210.69	13.107%	$238.3051	$238.31	$238.30	$238.30
Purchase #3	$136.87	3.813%	$142.0889	$142.09	$142.10	$142.10
Purchase #4	$239.82	13.555%	$272.3276	$272.33	$272.35	$272.30
Purchase #5	$200.41	11.243%	$222.9421	$222.94	$222.95	$222.90
Purchase #6	$67.56	6.376%	$71.8676	$71.87	$71.85	$71.90
Purchase #7	$88.36	11.525%	$98.5435	$98.54	$98.55	$98.50
7 purchase totals =	$1,042.06		$1,149.7337	$1,149.74	$1,149.75	$1,149.70