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	$100.85	8.254%	$109.1742	$109.17	$109.15	$109.20
Purchase #2	$242.27	5.857%	$256.4598	$256.46	$256.45	$256.50
Purchase #3	$37.51	3.659%	$38.8825	$38.88	$38.90	$38.90
Purchase #4	$154.31	5.243%	$162.4005	$162.40	$162.40	$162.40
Purchase #5	$86.34	11.263%	$96.0645	$96.06	$96.05	$96.10
Purchase #6	$236.80	9.417%	$259.0995	$259.10	$259.10	$259.10
Purchase #7	$212.47	10.818%	$235.455	$235.46	$235.45	$235.50
7 purchase totals =	$1,070.55		$1,157.5360	$1,157.53	$1,157.50	$1,157.70