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	$69.99	3.141%	$72.1884	$72.19	$72.20	$72.20
Purchase #2	$83.29	10.354%	$91.9138	$91.91	$91.90	$91.90
Purchase #3	$37.98	13.524%	$43.1164	$43.12	$43.10	$43.10
Purchase #4	$68.31	4.540%	$71.4113	$71.41	$71.40	$71.40
Purchase #5	$115.89	4.547%	$121.1595	$121.16	$121.15	$121.20
Purchase #6	$220.25	13.623%	$250.2547	$250.25	$250.25	$250.30
Purchase #7	$109.35	3.228%	$112.8798	$112.88	$112.90	$112.90
7 purchase totals =	$705.06		$762.9239	$762.92	$762.90	$763.00