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	$53.71	7.700%	$57.8457	$57.85	$57.85	$57.80
Purchase #2	$150.84	11.314%	$167.906	$167.91	$167.90	$167.90
Purchase #3	$240.36	13.842%	$273.6306	$273.63	$273.65	$273.60
Purchase #4	$153.61	5.759%	$162.4564	$162.46	$162.45	$162.50
Purchase #5	$141.45	3.658%	$146.6242	$146.62	$146.60	$146.60
Purchase #6	$146.79	4.821%	$153.8667	$153.87	$153.85	$153.90
Purchase #7	$55.86	11.707%	$62.3995	$62.40	$62.40	$62.40
7 purchase totals =	$942.62		$1,024.7291	$1,024.74	$1,024.70	$1,024.70