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	$179.47	11.831%	$200.7031	$200.70	$200.70	$200.70
Purchase #2	$121.89	6.856%	$130.2468	$130.25	$130.25	$130.20
Purchase #3	$156.50	7.658%	$168.4848	$168.48	$168.50	$168.50
Purchase #4	$84.59	6.128%	$89.7737	$89.77	$89.75	$89.80
Purchase #5	$212.73	4.502%	$222.3071	$222.31	$222.30	$222.30
Purchase #6	$99.94	9.224%	$109.1585	$109.16	$109.15	$109.20
Purchase #7	$168.95	3.630%	$175.0829	$175.08	$175.10	$175.10
7 purchase totals =	$1,024.07		$1,095.7569	$1,095.75	$1,095.75	$1,095.80