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	$187.71	9.616%	$205.7602	$205.76	$205.75	$205.80
Purchase #2	$85.50	5.244%	$89.9836	$89.98	$90.00	$90.00
Purchase #3	$164.62	10.650%	$182.152	$182.15	$182.15	$182.20
Purchase #4	$91.95	13.119%	$104.0129	$104.01	$104.00	$104.00
Purchase #5	$247.82	13.695%	$281.7589	$281.76	$281.75	$281.80
Purchase #6	$114.30	3.629%	$118.4479	$118.45	$118.45	$118.40
Purchase #7	$68.98	5.621%	$72.8574	$72.86	$72.85	$72.90
7 purchase totals =	$960.88		$1,054.9729	$1,054.97	$1,054.95	$1,055.10