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	$86.49	3.841%	$89.8121	$89.81	$89.80	$89.80
Purchase #2	$230.40	10.249%	$254.0137	$254.01	$254.00	$254.00
Purchase #3	$118.84	3.423%	$122.9079	$122.91	$122.90	$122.90
Purchase #4	$142.56	12.213%	$159.9709	$159.97	$159.95	$160.00
Purchase #5	$68.83	4.759%	$72.1056	$72.11	$72.10	$72.10
Purchase #6	$201.25	6.199%	$213.7255	$213.73	$213.75	$213.70
Purchase #7	$178.52	11.511%	$199.0694	$199.07	$199.05	$199.10
7 purchase totals =	$1,026.89		$1,111.6051	$1,111.61	$1,111.55	$1,111.60