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	$35.27	8.133%	$38.1385	$38.14	$38.15	$38.10
Purchase #2	$17.25	8.376%	$18.6949	$18.69	$18.70	$18.70
Purchase #3	$51.91	12.199%	$58.2425	$58.24	$58.25	$58.20
Purchase #4	$80.27	12.351%	$90.1841	$90.18	$90.20	$90.20
Purchase #5	$91.89	8.445%	$99.6501	$99.65	$99.65	$99.70
Purchase #6	$183.78	4.443%	$191.9453	$191.95	$191.95	$191.90
Purchase #7	$231.59	12.147%	$259.7212	$259.72	$259.70	$259.70
7 purchase totals =	$691.96		$756.5766	$756.57	$756.60	$756.50