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	$180.71	4.611%	$189.0425	$189.04	$189.05	$189.00
Purchase #2	$209.32	4.377%	$218.4819	$218.48	$218.50	$218.50
Purchase #3	$188.48	6.357%	$200.4617	$200.46	$200.45	$200.50
Purchase #4	$187.90	10.380%	$207.404	$207.40	$207.40	$207.40
Purchase #5	$57.65	3.829%	$59.8574	$59.86	$59.85	$59.90
Purchase #6	$232.77	7.464%	$250.144	$250.14	$250.15	$250.10
Purchase #7	$20.88	4.229%	$21.763	$21.76	$21.75	$21.80
7 purchase totals =	$1,077.71		$1,147.1545	$1,147.14	$1,147.15	$1,147.20