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	$90.30	4.530%	$94.3906	$94.39	$94.40	$94.40
Purchase #2	$71.92	4.835%	$75.3973	$75.40	$75.40	$75.40
Purchase #3	$86.56	5.451%	$91.2784	$91.28	$91.30	$91.30
Purchase #4	$169.84	6.498%	$180.8762	$180.88	$180.90	$180.90
Purchase #5	$35.39	5.357%	$37.2858	$37.29	$37.30	$37.30
Purchase #6	$151.58	10.257%	$167.1276	$167.13	$167.15	$167.10
Purchase #7	$130.59	5.167%	$137.3376	$137.34	$137.35	$137.30
7 purchase totals =	$736.18		$783.6935	$783.71	$783.80	$783.70