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	$33.33	8.856%	$36.2817	$36.28	$36.30	$36.30
Purchase #2	$19.67	7.803%	$21.2049	$21.20	$21.20	$21.20
Purchase #3	$34.72	10.329%	$38.3062	$38.31	$38.30	$38.30
Purchase #4	$184.54	6.645%	$196.8027	$196.80	$196.80	$196.80
Purchase #5	$207.73	5.584%	$219.3296	$219.33	$219.35	$219.30
Purchase #6	$156.99	6.728%	$167.5523	$167.55	$167.55	$167.60
Purchase #7	$89.81	11.142%	$99.8166	$99.82	$99.80	$99.80
7 purchase totals =	$726.79		$779.2940	$779.29	$779.30	$779.30