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	$152.60	9.499%	$167.0955	$167.10	$167.10	$167.10
Purchase #2	$54.29	4.780%	$56.8851	$56.89	$56.90	$56.90
Purchase #3	$209.69	9.251%	$229.0884	$229.09	$229.10	$229.10
Purchase #4	$200.77	3.869%	$208.5378	$208.54	$208.55	$208.50
Purchase #5	$44.36	5.487%	$46.794	$46.79	$46.80	$46.80
Purchase #6	$186.33	5.239%	$196.0918	$196.09	$196.10	$196.10
Purchase #7	$35.27	8.151%	$38.1449	$38.14	$38.15	$38.10
7 purchase totals =	$883.31		$942.6375	$942.64	$942.70	$942.60