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	$196.33	13.713%	$223.2527	$223.25	$223.25	$223.30
Purchase #2	$157.51	11.256%	$175.2393	$175.24	$175.25	$175.20
Purchase #3	$172.61	11.308%	$192.1287	$192.13	$192.15	$192.10
Purchase #4	$219.44	8.818%	$238.7902	$238.79	$238.80	$238.80
Purchase #5	$162.55	12.119%	$182.2494	$182.25	$182.25	$182.20
Purchase #6	$81.53	8.566%	$88.5139	$88.51	$88.50	$88.50
Purchase #7	$37.26	12.641%	$41.97	$41.97	$41.95	$42.00
7 purchase totals =	$1,027.23		$1,142.1442	$1,142.14	$1,142.15	$1,142.10