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	$78.30	6.408%	$83.3175	$83.32	$83.30	$83.30
Purchase #2	$168.52	13.433%	$191.1573	$191.16	$191.15	$191.20
Purchase #3	$91.74	9.606%	$100.5525	$100.55	$100.55	$100.60
Purchase #4	$23.75	7.428%	$25.5142	$25.51	$25.50	$25.50
Purchase #5	$174.27	3.568%	$180.488	$180.49	$180.50	$180.50
Purchase #6	$190.61	12.650%	$214.7222	$214.72	$214.70	$214.70
Purchase #7	$190.28	8.383%	$206.2312	$206.23	$206.25	$206.20
7 purchase totals =	$917.47		$1,001.9829	$1,001.98	$1,001.95	$1,002.00