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	$170.65	6.552%	$181.831	$181.83	$181.85	$181.80
Purchase #2	$132.42	11.469%	$147.6072	$147.61	$147.60	$147.60
Purchase #3	$20.97	3.608%	$21.7266	$21.73	$21.75	$21.70
Purchase #4	$114.30	3.335%	$118.1119	$118.11	$118.10	$118.10
Purchase #5	$182.59	3.242%	$188.5096	$188.51	$188.50	$188.50
Purchase #6	$227.26	6.182%	$241.3092	$241.31	$241.30	$241.30
Purchase #7	$222.60	10.134%	$245.1583	$245.16	$245.15	$245.20
7 purchase totals =	$1,070.79		$1,144.2538	$1,144.26	$1,144.25	$1,144.20