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	$167.29	9.134%	$182.5703	$182.57	$182.55	$182.60
Purchase #2	$69.33	13.326%	$78.5689	$78.57	$78.55	$78.60
Purchase #3	$110.95	5.543%	$117.1	$117.10	$117.10	$117.10
Purchase #4	$95.72	5.861%	$101.3301	$101.33	$101.35	$101.30
Purchase #5	$190.29	10.136%	$209.5778	$209.58	$209.60	$209.60
Purchase #6	$206.53	13.165%	$233.7197	$233.72	$233.70	$233.70
Purchase #7	$247.75	8.360%	$268.4619	$268.46	$268.45	$268.50
7 purchase totals =	$1,087.86		$1,191.3287	$1,191.33	$1,191.30	$1,191.40