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	$102.85	4.828%	$107.8156	$107.82	$107.80	$107.80
Purchase #2	$29.37	11.616%	$32.7816	$32.78	$32.80	$32.80
Purchase #3	$79.92	11.631%	$89.2155	$89.22	$89.20	$89.20
Purchase #4	$128.91	10.481%	$142.4211	$142.42	$142.40	$142.40
Purchase #5	$245.46	11.301%	$273.1994	$273.20	$273.20	$273.20
Purchase #6	$152.81	12.828%	$172.4125	$172.41	$172.40	$172.40
Purchase #7	$219.65	7.209%	$235.4846	$235.48	$235.50	$235.50
7 purchase totals =	$958.97		$1,053.3303	$1,053.33	$1,053.30	$1,053.30