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	$53.66	8.195%	$58.0574	$58.06	$58.05	$58.10
Purchase #2	$152.40	6.504%	$162.3121	$162.31	$162.30	$162.30
Purchase #3	$71.54	8.782%	$77.8226	$77.82	$77.80	$77.80
Purchase #4	$144.93	12.367%	$162.8535	$162.85	$162.85	$162.90
Purchase #5	$168.43	4.580%	$176.1441	$176.14	$176.15	$176.10
Purchase #6	$31.92	12.225%	$35.8222	$35.82	$35.80	$35.80
Purchase #7	$83.37	7.365%	$89.5102	$89.51	$89.50	$89.50
7 purchase totals =	$706.25		$762.5221	$762.51	$762.45	$762.50