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	$201.28	10.498%	$222.4104	$222.41	$222.40	$222.40
Purchase #2	$182.63	13.561%	$207.3965	$207.40	$207.40	$207.40
Purchase #3	$36.42	11.615%	$40.6502	$40.65	$40.65	$40.70
Purchase #4	$134.38	6.679%	$143.3552	$143.36	$143.35	$143.40
Purchase #5	$26.73	12.860%	$30.1675	$30.17	$30.15	$30.20
Purchase #6	$130.59	11.282%	$145.3232	$145.32	$145.30	$145.30
Purchase #7	$170.29	11.226%	$189.4068	$189.41	$189.40	$189.40
7 purchase totals =	$882.32		$978.7098	$978.72	$978.65	$978.80