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	$209.82	5.578%	$221.5238	$221.52	$221.50	$221.50
Purchase #2	$215.90	12.132%	$242.093	$242.09	$242.10	$242.10
Purchase #3	$41.30	10.162%	$45.4969	$45.50	$45.50	$45.50
Purchase #4	$131.27	13.595%	$149.1162	$149.12	$149.10	$149.10
Purchase #5	$133.83	6.774%	$142.8956	$142.90	$142.90	$142.90
Purchase #6	$191.65	11.578%	$213.8392	$213.84	$213.85	$213.80
Purchase #7	$240.40	6.380%	$255.7375	$255.74	$255.75	$255.70
7 purchase totals =	$1,164.17		$1,270.7022	$1,270.71	$1,270.70	$1,270.60