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	$29.42	11.279%	$32.7383	$32.74	$32.75	$32.70
Purchase #2	$236.49	9.843%	$259.7677	$259.77	$259.75	$259.80
Purchase #3	$59.57	7.451%	$64.0086	$64.01	$64.00	$64.00
Purchase #4	$40.32	6.328%	$42.8714	$42.87	$42.85	$42.90
Purchase #5	$170.43	4.756%	$178.5357	$178.54	$178.55	$178.50
Purchase #6	$144.37	11.812%	$161.423	$161.42	$161.40	$161.40
Purchase #7	$54.26	6.323%	$57.6909	$57.69	$57.70	$57.70
7 purchase totals =	$734.86		$797.0356	$797.04	$797.00	$797.00