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	$248.51	7.531%	$267.2253	$267.23	$267.25	$267.20
Purchase #2	$151.60	4.596%	$158.5675	$158.57	$158.55	$158.60
Purchase #3	$39.50	6.633%	$42.12	$42.12	$42.10	$42.10
Purchase #4	$77.81	3.253%	$80.3412	$80.34	$80.35	$80.30
Purchase #5	$67.93	5.510%	$71.6729	$71.67	$71.65	$71.70
Purchase #6	$25.28	11.280%	$28.1316	$28.13	$28.15	$28.10
Purchase #7	$118.59	11.549%	$132.286	$132.29	$132.30	$132.30
7 purchase totals =	$729.22		$780.3445	$780.35	$780.35	$780.30