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	$67.32	4.115%	$70.0902	$70.09	$70.10	$70.10
Purchase #2	$121.55	5.856%	$128.668	$128.67	$128.65	$128.70
Purchase #3	$55.45	11.132%	$61.6227	$61.62	$61.60	$61.60
Purchase #4	$154.65	9.663%	$169.5938	$169.59	$169.60	$169.60
Purchase #5	$127.74	13.375%	$144.8252	$144.83	$144.85	$144.80
Purchase #6	$29.80	13.860%	$33.9303	$33.93	$33.95	$33.90
Purchase #7	$148.75	10.861%	$164.9057	$164.91	$164.90	$164.90
7 purchase totals =	$705.26		$773.6359	$773.64	$773.65	$773.60