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	$90.44	4.801%	$94.782	$94.78	$94.80	$94.80
Purchase #2	$197.64	13.299%	$223.9241	$223.92	$223.90	$223.90
Purchase #3	$84.62	6.252%	$89.9104	$89.91	$89.90	$89.90
Purchase #4	$75.99	6.626%	$81.0251	$81.03	$81.05	$81.00
Purchase #5	$135.65	10.696%	$150.1591	$150.16	$150.15	$150.20
Purchase #6	$196.90	12.406%	$221.3274	$221.33	$221.35	$221.30
Purchase #7	$213.45	4.442%	$222.9314	$222.93	$222.95	$222.90
7 purchase totals =	$994.69		$1,084.0595	$1,084.06	$1,084.10	$1,084.00