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	$175.74	7.191%	$188.3775	$188.38	$188.40	$188.40
Purchase #2	$164.45	9.129%	$179.4626	$179.46	$179.45	$179.50
Purchase #3	$67.98	8.251%	$73.589	$73.59	$73.60	$73.60
Purchase #4	$131.57	13.188%	$148.9215	$148.92	$148.90	$148.90
Purchase #5	$198.38	5.874%	$210.0328	$210.03	$210.05	$210.00
Purchase #6	$105.73	6.293%	$112.3836	$112.38	$112.40	$112.40
Purchase #7	$241.46	8.439%	$261.8368	$261.84	$261.85	$261.80
7 purchase totals =	$1,085.31		$1,174.6038	$1,174.60	$1,174.65	$1,174.60