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	$86.90	12.832%	$98.051	$98.05	$98.05	$98.10
Purchase #2	$84.33	7.339%	$90.519	$90.52	$90.50	$90.50
Purchase #3	$229.55	7.123%	$245.9008	$245.90	$245.90	$245.90
Purchase #4	$72.42	8.710%	$78.7278	$78.73	$78.75	$78.70
Purchase #5	$81.55	7.453%	$87.6279	$87.63	$87.65	$87.60
Purchase #6	$5.81	4.494%	$6.0711	$6.07	$6.05	$6.10
Purchase #7	$167.77	7.560%	$180.4534	$180.45	$180.45	$180.50
7 purchase totals =	$728.33		$787.3510	$787.35	$787.35	$787.40