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	$188.37	13.596%	$213.9808	$213.98	$214.00	$214.00
Purchase #2	$91.50	13.479%	$103.8333	$103.83	$103.85	$103.80
Purchase #3	$75.63	7.638%	$81.4066	$81.41	$81.40	$81.40
Purchase #4	$192.73	13.603%	$218.9471	$218.95	$218.95	$218.90
Purchase #5	$30.67	4.519%	$32.056	$32.06	$32.05	$32.10
Purchase #6	$86.29	10.625%	$95.4583	$95.46	$95.45	$95.50
Purchase #7	$174.67	12.531%	$196.5579	$196.56	$196.55	$196.60
7 purchase totals =	$839.86		$942.2400	$942.25	$942.25	$942.30