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	$240.46	9.568%	$263.4672	$263.47	$263.45	$263.50
Purchase #2	$74.32	3.853%	$77.1835	$77.18	$77.20	$77.20
Purchase #3	$143.90	13.135%	$162.8013	$162.80	$162.80	$162.80
Purchase #4	$19.59	13.453%	$22.2254	$22.23	$22.25	$22.20
Purchase #5	$89.92	10.754%	$99.59	$99.59	$99.60	$99.60
Purchase #6	$93.43	11.642%	$104.3071	$104.31	$104.30	$104.30
Purchase #7	$142.41	10.146%	$156.8589	$156.86	$156.85	$156.90
7 purchase totals =	$804.03		$886.4334	$886.44	$886.45	$886.50