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	$179.75	3.829%	$186.6326	$186.63	$186.65	$186.60
Purchase #2	$81.29	11.448%	$90.5961	$90.60	$90.60	$90.60
Purchase #3	$167.92	6.350%	$178.5829	$178.58	$178.60	$178.60
Purchase #4	$103.96	7.405%	$111.6582	$111.66	$111.65	$111.70
Purchase #5	$211.40	8.655%	$229.6967	$229.70	$229.70	$229.70
Purchase #6	$236.80	11.351%	$263.6792	$263.68	$263.70	$263.70
Purchase #7	$145.66	11.487%	$162.392	$162.39	$162.40	$162.40
7 purchase totals =	$1,126.78		$1,223.2377	$1,223.24	$1,223.30	$1,223.30