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	$70.38	4.742%	$73.7174	$73.72	$73.70	$73.70
Purchase #2	$158.92	3.360%	$164.2597	$164.26	$164.25	$164.30
Purchase #3	$148.26	5.860%	$156.948	$156.95	$156.95	$156.90
Purchase #4	$106.73	3.540%	$110.5082	$110.51	$110.50	$110.50
Purchase #5	$107.56	10.872%	$119.2539	$119.25	$119.25	$119.30
Purchase #6	$42.43	7.798%	$45.7387	$45.74	$45.75	$45.70
Purchase #7	$211.49	8.683%	$229.8537	$229.85	$229.85	$229.90
7 purchase totals =	$845.77		$900.2796	$900.28	$900.25	$900.30