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	$48.71	6.539%	$51.8951	$51.90	$51.90	$51.90
Purchase #2	$29.59	8.316%	$32.0507	$32.05	$32.05	$32.10
Purchase #3	$89.87	5.792%	$95.0753	$95.08	$95.10	$95.10
Purchase #4	$98.52	4.411%	$102.8657	$102.87	$102.85	$102.90
Purchase #5	$161.91	4.731%	$169.57	$169.57	$169.55	$169.60
Purchase #6	$92.49	3.279%	$95.5227	$95.52	$95.50	$95.50
Purchase #7	$129.76	11.263%	$144.3749	$144.37	$144.35	$144.40
7 purchase totals =	$650.85		$691.3544	$691.36	$691.30	$691.50