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	$26.84	8.658%	$29.1638	$29.16	$29.15	$29.20
Purchase #2	$62.72	11.192%	$69.7396	$69.74	$69.75	$69.70
Purchase #3	$113.49	3.663%	$117.6471	$117.65	$117.65	$117.60
Purchase #4	$72.58	8.687%	$78.885	$78.89	$78.90	$78.90
Purchase #5	$98.59	3.597%	$102.1363	$102.14	$102.15	$102.10
Purchase #6	$148.59	11.148%	$165.1548	$165.15	$165.15	$165.20
Purchase #7	$175.93	13.781%	$200.1749	$200.17	$200.15	$200.20
7 purchase totals =	$698.74		$762.9015	$762.90	$762.90	$762.90