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	$219.59	11.360%	$244.5354	$244.54	$244.55	$244.50
Purchase #2	$64.86	9.655%	$71.1222	$71.12	$71.10	$71.10
Purchase #3	$181.49	10.119%	$199.855	$199.86	$199.85	$199.90
Purchase #4	$33.53	6.866%	$35.8322	$35.83	$35.85	$35.80
Purchase #5	$79.94	6.638%	$85.2464	$85.25	$85.25	$85.20
Purchase #6	$49.76	7.841%	$53.6617	$53.66	$53.65	$53.70
Purchase #7	$168.76	11.604%	$188.3429	$188.34	$188.35	$188.30
7 purchase totals =	$797.93		$878.5958	$878.60	$878.60	$878.50