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	$133.62	13.486%	$151.64	$151.64	$151.65	$151.60
Purchase #2	$6.48	11.275%	$7.2106	$7.21	$7.20	$7.20
Purchase #3	$10.40	4.759%	$10.8949	$10.89	$10.90	$10.90
Purchase #4	$96.75	4.650%	$101.2489	$101.25	$101.25	$101.20
Purchase #5	$210.34	4.228%	$219.2332	$219.23	$219.25	$219.20
Purchase #6	$78.92	3.675%	$81.8203	$81.82	$81.80	$81.80
Purchase #7	$133.31	5.670%	$140.8687	$140.87	$140.85	$140.90
7 purchase totals =	$669.82		$712.9166	$712.91	$712.90	$712.80