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	$158.99	8.527%	$172.5471	$172.55	$172.55	$172.50
Purchase #2	$144.51	11.290%	$160.8252	$160.83	$160.85	$160.80
Purchase #3	$69.56	11.390%	$77.4829	$77.48	$77.50	$77.50
Purchase #4	$107.28	4.716%	$112.3393	$112.34	$112.35	$112.30
Purchase #5	$31.35	12.496%	$35.2675	$35.27	$35.25	$35.30
Purchase #6	$78.65	10.153%	$86.6353	$86.64	$86.65	$86.60
Purchase #7	$99.48	4.687%	$104.1426	$104.14	$104.15	$104.10
7 purchase totals =	$689.82		$749.2399	$749.25	$749.30	$749.10