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	$180.94	10.304%	$199.5841	$199.58	$199.60	$199.60
Purchase #2	$64.53	8.828%	$70.2267	$70.23	$70.25	$70.20
Purchase #3	$91.82	3.346%	$94.8923	$94.89	$94.90	$94.90
Purchase #4	$111.66	7.599%	$120.145	$120.15	$120.15	$120.10
Purchase #5	$191.82	8.151%	$207.4552	$207.46	$207.45	$207.50
Purchase #6	$206.31	9.785%	$226.4974	$226.50	$226.50	$226.50
Purchase #7	$137.84	3.539%	$142.7182	$142.72	$142.70	$142.70
7 purchase totals =	$984.92		$1,061.5189	$1,061.53	$1,061.55	$1,061.50