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	$193.28	13.245%	$218.8799	$218.88	$218.90	$218.90
Purchase #2	$47.53	4.598%	$49.7154	$49.72	$49.70	$49.70
Purchase #3	$187.76	9.126%	$204.895	$204.90	$204.90	$204.90
Purchase #4	$245.49	11.391%	$273.4538	$273.45	$273.45	$273.50
Purchase #5	$160.30	7.853%	$172.8884	$172.89	$172.90	$172.90
Purchase #6	$72.95	9.300%	$79.7344	$79.73	$79.75	$79.70
Purchase #7	$31.28	6.522%	$33.3201	$33.32	$33.30	$33.30
7 purchase totals =	$938.59		$1,032.8870	$1,032.89	$1,032.90	$1,032.90