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	$41.73	7.278%	$44.7671	$44.77	$44.75	$44.80
Purchase #2	$229.59	5.144%	$241.4001	$241.40	$241.40	$241.40
Purchase #3	$124.72	3.269%	$128.7971	$128.80	$128.80	$128.80
Purchase #4	$137.84	5.427%	$145.3206	$145.32	$145.30	$145.30
Purchase #5	$13.51	8.159%	$14.6123	$14.61	$14.60	$14.60
Purchase #6	$93.72	6.472%	$99.7856	$99.79	$99.80	$99.80
Purchase #7	$148.66	9.129%	$162.2312	$162.23	$162.25	$162.20
7 purchase totals =	$789.77		$836.9140	$836.92	$836.90	$836.90