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	$35.61	5.611%	$37.6081	$37.61	$37.60	$37.60
Purchase #2	$92.54	4.311%	$96.5294	$96.53	$96.55	$96.50
Purchase #3	$145.67	10.470%	$160.9216	$160.92	$160.90	$160.90
Purchase #4	$146.54	10.784%	$162.3429	$162.34	$162.35	$162.30
Purchase #5	$120.91	11.706%	$135.0637	$135.06	$135.05	$135.10
Purchase #6	$81.82	11.710%	$91.4011	$91.40	$91.40	$91.40
Purchase #7	$70.41	10.573%	$77.8544	$77.85	$77.85	$77.90
7 purchase totals =	$693.50		$761.7212	$761.71	$761.70	$761.70