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	$243.97	13.152%	$276.0569	$276.06	$276.05	$276.10
Purchase #2	$115.82	10.575%	$128.068	$128.07	$128.05	$128.10
Purchase #3	$212.50	3.141%	$219.1746	$219.17	$219.15	$219.20
Purchase #4	$127.88	13.360%	$144.9648	$144.96	$144.95	$145.00
Purchase #5	$233.44	4.503%	$243.9518	$243.95	$243.95	$244.00
Purchase #6	$41.28	3.870%	$42.8775	$42.88	$42.90	$42.90
Purchase #7	$113.42	4.734%	$118.7893	$118.79	$118.80	$118.80
7 purchase totals =	$1,088.31		$1,173.8829	$1,173.88	$1,173.85	$1,174.10