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	$169.45	10.755%	$187.6743	$187.67	$187.65	$187.70
Purchase #2	$209.45	4.685%	$219.2627	$219.26	$219.25	$219.30
Purchase #3	$24.57	9.402%	$26.8801	$26.88	$26.90	$26.90
Purchase #4	$51.76	7.409%	$55.5949	$55.59	$55.60	$55.60
Purchase #5	$137.72	9.318%	$150.5527	$150.55	$150.55	$150.60
Purchase #6	$100.84	11.663%	$112.601	$112.60	$112.60	$112.60
Purchase #7	$35.68	4.156%	$37.1629	$37.16	$37.15	$37.20
7 purchase totals =	$729.47		$789.7286	$789.71	$789.70	$789.90