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	$174.36	12.445%	$196.0591	$196.06	$196.05	$196.10
Purchase #2	$145.40	6.843%	$155.3497	$155.35	$155.35	$155.30
Purchase #3	$82.27	10.337%	$90.7742	$90.77	$90.75	$90.80
Purchase #4	$228.43	13.593%	$259.4805	$259.48	$259.50	$259.50
Purchase #5	$159.97	9.201%	$174.6888	$174.69	$174.70	$174.70
Purchase #6	$5.86	3.446%	$6.0619	$6.06	$6.05	$6.10
Purchase #7	$120.40	7.278%	$129.1627	$129.16	$129.15	$129.20
7 purchase totals =	$916.69		$1,011.5769	$1,011.57	$1,011.55	$1,011.70