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	$159.28	13.274%	$180.4228	$180.42	$180.40	$180.40
Purchase #2	$149.82	8.727%	$162.8948	$162.89	$162.90	$162.90
Purchase #3	$27.94	6.596%	$29.7829	$29.78	$29.80	$29.80
Purchase #4	$103.62	11.814%	$115.8617	$115.86	$115.85	$115.90
Purchase #5	$224.25	5.362%	$236.2743	$236.27	$236.25	$236.30
Purchase #6	$137.42	13.648%	$156.1751	$156.18	$156.20	$156.20
Purchase #7	$163.50	13.181%	$185.0509	$185.05	$185.05	$185.10
7 purchase totals =	$965.83		$1,066.4625	$1,066.45	$1,066.45	$1,066.60