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	$35.84	3.841%	$37.2166	$37.22	$37.20	$37.20
Purchase #2	$25.53	7.395%	$27.4179	$27.42	$27.40	$27.40
Purchase #3	$46.96	12.850%	$52.9944	$52.99	$53.00	$53.00
Purchase #4	$244.74	8.174%	$264.745	$264.75	$264.75	$264.70
Purchase #5	$233.82	11.727%	$261.2401	$261.24	$261.25	$261.20
Purchase #6	$248.74	6.789%	$265.627	$265.63	$265.65	$265.60
Purchase #7	$183.63	4.353%	$191.6234	$191.62	$191.60	$191.60
7 purchase totals =	$1,019.26		$1,100.8644	$1,100.87	$1,100.85	$1,100.70