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	$162.33	10.345%	$179.123	$179.12	$179.10	$179.10
Purchase #2	$173.55	3.659%	$179.9002	$179.90	$179.90	$179.90
Purchase #3	$152.71	4.662%	$159.8293	$159.83	$159.85	$159.80
Purchase #4	$212.71	12.133%	$238.5181	$238.52	$238.50	$238.50
Purchase #5	$81.31	4.705%	$85.1356	$85.14	$85.15	$85.10
Purchase #6	$133.31	6.369%	$141.8005	$141.80	$141.80	$141.80
Purchase #7	$35.74	11.480%	$39.843	$39.84	$39.85	$39.80
7 purchase totals =	$951.66		$1,024.1497	$1,024.15	$1,024.15	$1,024.00