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	$167.62	13.355%	$190.0057	$190.01	$190.00	$190.00
Purchase #2	$162.36	11.840%	$181.5834	$181.58	$181.60	$181.60
Purchase #3	$194.53	7.702%	$209.5127	$209.51	$209.50	$209.50
Purchase #4	$79.29	12.593%	$89.275	$89.28	$89.30	$89.30
Purchase #5	$80.56	7.543%	$86.6366	$86.64	$86.65	$86.60
Purchase #6	$178.31	6.287%	$189.5203	$189.52	$189.50	$189.50
Purchase #7	$230.48	8.683%	$250.4926	$250.49	$250.50	$250.50
7 purchase totals =	$1,093.15		$1,197.0263	$1,197.03	$1,197.05	$1,197.00