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	$157.89	11.404%	$175.8958	$175.90	$175.90	$175.90
Purchase #2	$223.32	13.464%	$253.3878	$253.39	$253.40	$253.40
Purchase #3	$69.38	11.537%	$77.3844	$77.38	$77.40	$77.40
Purchase #4	$25.33	7.598%	$27.2546	$27.25	$27.25	$27.30
Purchase #5	$103.76	8.803%	$112.894	$112.89	$112.90	$112.90
Purchase #6	$121.44	8.192%	$131.3884	$131.39	$131.40	$131.40
Purchase #7	$114.74	9.189%	$125.2835	$125.28	$125.30	$125.30
7 purchase totals =	$815.86		$903.4885	$903.48	$903.55	$903.60