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	$142.52	5.330%	$150.1163	$150.12	$150.10	$150.10
Purchase #2	$71.46	13.268%	$80.9413	$80.94	$80.95	$80.90
Purchase #3	$154.48	13.627%	$175.531	$175.53	$175.55	$175.50
Purchase #4	$78.80	4.384%	$82.2546	$82.25	$82.25	$82.30
Purchase #5	$243.93	7.363%	$261.8906	$261.89	$261.90	$261.90
Purchase #6	$134.70	4.298%	$140.4894	$140.49	$140.50	$140.50
Purchase #7	$102.68	7.762%	$110.65	$110.65	$110.65	$110.70
7 purchase totals =	$928.57		$1,001.8732	$1,001.87	$1,001.90	$1,001.90