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	$101.84	7.117%	$109.088	$109.09	$109.10	$109.10
Purchase #2	$82.96	7.858%	$89.479	$89.48	$89.50	$89.50
Purchase #3	$73.76	3.511%	$76.3497	$76.35	$76.35	$76.30
Purchase #4	$159.79	11.244%	$177.7568	$177.76	$177.75	$177.80
Purchase #5	$101.42	6.294%	$107.8034	$107.80	$107.80	$107.80
Purchase #6	$209.49	6.715%	$223.5573	$223.56	$223.55	$223.60
Purchase #7	$80.69	10.870%	$89.461	$89.46	$89.45	$89.50
7 purchase totals =	$809.95		$873.4952	$873.50	$873.50	$873.60