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	$89.35	3.437%	$92.421	$92.42	$92.40	$92.40
Purchase #2	$178.82	5.618%	$188.8661	$188.87	$188.85	$188.90
Purchase #3	$101.86	3.242%	$105.1623	$105.16	$105.15	$105.20
Purchase #4	$59.54	5.184%	$62.6266	$62.63	$62.65	$62.60
Purchase #5	$100.69	13.454%	$114.2368	$114.24	$114.25	$114.20
Purchase #6	$57.43	8.108%	$62.0864	$62.09	$62.10	$62.10
Purchase #7	$22.56	7.347%	$24.2175	$24.22	$24.20	$24.20
7 purchase totals =	$610.25		$649.6167	$649.63	$649.60	$649.60