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	$69.26	3.443%	$71.6446	$71.64	$71.65	$71.60
Purchase #2	$93.54	12.760%	$105.4757	$105.48	$105.50	$105.50
Purchase #3	$7.66	11.397%	$8.533	$8.53	$8.55	$8.50
Purchase #4	$5.62	10.315%	$6.1997	$6.20	$6.20	$6.20
Purchase #5	$215.90	3.133%	$222.6641	$222.66	$222.65	$222.70
Purchase #6	$50.46	10.135%	$55.5741	$55.57	$55.55	$55.60
Purchase #7	$100.52	7.543%	$108.1022	$108.10	$108.10	$108.10
7 purchase totals =	$542.96		$578.1934	$578.18	$578.20	$578.20