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	$159.80	5.279%	$168.2358	$168.24	$168.25	$168.20
Purchase #2	$167.97	11.543%	$187.3588	$187.36	$187.35	$187.40
Purchase #3	$57.73	3.268%	$59.6166	$59.62	$59.60	$59.60
Purchase #4	$117.44	4.852%	$123.1382	$123.14	$123.15	$123.10
Purchase #5	$162.39	5.230%	$170.883	$170.88	$170.90	$170.90
Purchase #6	$191.84	7.572%	$206.3661	$206.37	$206.35	$206.40
Purchase #7	$168.32	13.176%	$190.4978	$190.50	$190.50	$190.50
7 purchase totals =	$1,025.49		$1,106.0963	$1,106.11	$1,106.10	$1,106.10