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	$225.57	4.739%	$236.2598	$236.26	$236.25	$236.30
Purchase #2	$61.70	6.190%	$65.5192	$65.52	$65.50	$65.50
Purchase #3	$24.57	13.683%	$27.9319	$27.93	$27.95	$27.90
Purchase #4	$210.62	10.644%	$233.0384	$233.04	$233.05	$233.00
Purchase #5	$79.85	3.155%	$82.3693	$82.37	$82.35	$82.40
Purchase #6	$227.42	10.688%	$251.7266	$251.73	$251.75	$251.70
Purchase #7	$181.70	10.228%	$200.2843	$200.28	$200.30	$200.30
7 purchase totals =	$1,011.43		$1,097.1295	$1,097.13	$1,097.15	$1,097.10