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	$123.58	4.426%	$129.0497	$129.05	$129.05	$129.00
Purchase #2	$110.27	7.338%	$118.3616	$118.36	$118.35	$118.40
Purchase #3	$173.97	6.440%	$185.1737	$185.17	$185.15	$185.20
Purchase #4	$152.69	6.608%	$162.7798	$162.78	$162.80	$162.80
Purchase #5	$162.51	4.316%	$169.5239	$169.52	$169.50	$169.50
Purchase #6	$154.30	3.345%	$159.4613	$159.46	$159.45	$159.50
Purchase #7	$131.84	9.670%	$144.5889	$144.59	$144.60	$144.60
7 purchase totals =	$1,009.16		$1,068.9389	$1,068.93	$1,068.90	$1,069.00