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	$39.41	6.156%	$41.8361	$41.84	$41.85	$41.80
Purchase #2	$238.58	13.296%	$270.3016	$270.30	$270.30	$270.30
Purchase #3	$24.90	13.673%	$28.3046	$28.30	$28.30	$28.30
Purchase #4	$52.37	3.282%	$54.0888	$54.09	$54.10	$54.10
Purchase #5	$147.83	11.303%	$164.5392	$164.54	$164.55	$164.50
Purchase #6	$239.48	10.303%	$264.1536	$264.15	$264.15	$264.20
Purchase #7	$210.53	3.763%	$218.4522	$218.45	$218.45	$218.50
7 purchase totals =	$953.10		$1,041.6761	$1,041.67	$1,041.70	$1,041.70