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	$123.79	4.586%	$129.467	$129.47	$129.45	$129.50
Purchase #2	$164.75	4.569%	$172.2774	$172.28	$172.30	$172.30
Purchase #3	$194.71	7.152%	$208.6357	$208.64	$208.65	$208.60
Purchase #4	$200.84	3.816%	$208.5041	$208.50	$208.50	$208.50
Purchase #5	$72.78	6.415%	$77.4488	$77.45	$77.45	$77.40
Purchase #6	$116.69	12.339%	$131.0884	$131.09	$131.10	$131.10
Purchase #7	$168.29	7.474%	$180.868	$180.87	$180.85	$180.90
7 purchase totals =	$1,041.85		$1,108.2894	$1,108.30	$1,108.30	$1,108.30