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	$81.38	10.414%	$89.8549	$89.85	$89.85	$89.90
Purchase #2	$105.62	5.788%	$111.7333	$111.73	$111.75	$111.70
Purchase #3	$137.53	3.535%	$142.3917	$142.39	$142.40	$142.40
Purchase #4	$107.69	5.170%	$113.2576	$113.26	$113.25	$113.30
Purchase #5	$63.71	5.714%	$67.3504	$67.35	$67.35	$67.40
Purchase #6	$215.77	9.375%	$235.9984	$236.00	$236.00	$236.00
Purchase #7	$242.66	10.567%	$268.3019	$268.30	$268.30	$268.30
7 purchase totals =	$954.36		$1,028.8882	$1,028.88	$1,028.90	$1,029.00