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	$165.26	3.618%	$171.2391	$171.24	$171.25	$171.20
Purchase #2	$225.26	10.768%	$249.516	$249.52	$249.50	$249.50
Purchase #3	$98.76	3.549%	$102.265	$102.27	$102.25	$102.30
Purchase #4	$45.87	13.238%	$51.9423	$51.94	$51.95	$51.90
Purchase #5	$18.66	7.331%	$20.028	$20.03	$20.05	$20.00
Purchase #6	$88.76	8.466%	$96.2744	$96.27	$96.25	$96.30
Purchase #7	$64.33	4.600%	$67.2892	$67.29	$67.30	$67.30
7 purchase totals =	$706.90		$758.5540	$758.56	$758.55	$758.50