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	$174.53	4.829%	$182.9581	$182.96	$182.95	$183.00
Purchase #2	$127.79	4.502%	$133.5431	$133.54	$133.55	$133.50
Purchase #3	$58.51	9.591%	$64.1217	$64.12	$64.10	$64.10
Purchase #4	$37.48	12.493%	$42.1624	$42.16	$42.15	$42.20
Purchase #5	$163.98	10.571%	$181.3143	$181.31	$181.30	$181.30
Purchase #6	$96.65	9.556%	$105.8859	$105.89	$105.90	$105.90
Purchase #7	$230.59	6.738%	$246.1272	$246.13	$246.15	$246.10
7 purchase totals =	$889.53		$956.1127	$956.11	$956.10	$956.10