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	$53.42	4.251%	$55.6909	$55.69	$55.70	$55.70
Purchase #2	$36.47	3.780%	$37.8486	$37.85	$37.85	$37.80
Purchase #3	$6.49	8.170%	$7.0202	$7.02	$7.00	$7.00
Purchase #4	$27.77	13.334%	$31.4729	$31.47	$31.45	$31.50
Purchase #5	$13.97	13.418%	$15.8445	$15.84	$15.85	$15.80
Purchase #6	$160.93	12.873%	$181.6465	$181.65	$181.65	$181.60
Purchase #7	$74.33	6.133%	$78.8887	$78.89	$78.90	$78.90
7 purchase totals =	$373.38		$408.4123	$408.41	$408.40	$408.30