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	$34.30	11.850%	$38.3646	$38.36	$38.35	$38.40
Purchase #2	$83.34	13.480%	$94.5742	$94.57	$94.55	$94.60
Purchase #3	$144.63	4.635%	$151.3336	$151.33	$151.35	$151.30
Purchase #4	$88.82	10.667%	$98.2944	$98.29	$98.30	$98.30
Purchase #5	$174.26	5.450%	$183.7572	$183.76	$183.75	$183.80
Purchase #6	$190.75	4.610%	$199.5436	$199.54	$199.55	$199.50
Purchase #7	$108.32	3.107%	$111.6855	$111.69	$111.70	$111.70
7 purchase totals =	$824.42		$877.5531	$877.54	$877.55	$877.60