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	$73.77	11.284%	$82.0942	$82.09	$82.10	$82.10
Purchase #2	$142.36	11.863%	$159.2482	$159.25	$159.25	$159.20
Purchase #3	$115.53	11.863%	$129.2353	$129.24	$129.25	$129.20
Purchase #4	$6.90	10.752%	$7.6419	$7.64	$7.65	$7.60
Purchase #5	$38.73	10.847%	$42.931	$42.93	$42.95	$42.90
Purchase #6	$170.52	12.638%	$192.0703	$192.07	$192.05	$192.10
Purchase #7	$165.33	3.764%	$171.553	$171.55	$171.55	$171.60
7 purchase totals =	$713.14		$784.7739	$784.77	$784.80	$784.70