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	$27.64	10.439%	$30.5253	$30.53	$30.55	$30.50
Purchase #2	$38.85	10.166%	$42.7995	$42.80	$42.80	$42.80
Purchase #3	$227.88	11.270%	$253.5621	$253.56	$253.55	$253.60
Purchase #4	$151.43	8.608%	$164.4651	$164.47	$164.45	$164.50
Purchase #5	$95.97	7.543%	$103.209	$103.21	$103.20	$103.20
Purchase #6	$234.77	3.572%	$243.156	$243.16	$243.15	$243.20
Purchase #7	$248.40	7.834%	$267.8597	$267.86	$267.85	$267.90
7 purchase totals =	$1,024.94		$1,105.5767	$1,105.59	$1,105.55	$1,105.70