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	$166.56	8.822%	$181.2539	$181.25	$181.25	$181.30
Purchase #2	$168.28	11.747%	$188.0479	$188.05	$188.05	$188.00
Purchase #3	$174.66	6.660%	$186.2924	$186.29	$186.30	$186.30
Purchase #4	$147.31	10.234%	$162.3857	$162.39	$162.40	$162.40
Purchase #5	$177.74	3.571%	$184.0871	$184.09	$184.10	$184.10
Purchase #6	$106.79	4.757%	$111.87	$111.87	$111.85	$111.90
Purchase #7	$21.58	6.114%	$22.8994	$22.90	$22.90	$22.90
7 purchase totals =	$962.92		$1,036.8364	$1,036.84	$1,036.85	$1,036.90