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	$101.95	9.660%	$111.7984	$111.80	$111.80	$111.80
Purchase #2	$93.59	3.552%	$96.9143	$96.91	$96.90	$96.90
Purchase #3	$30.66	3.723%	$31.8015	$31.80	$31.80	$31.80
Purchase #4	$241.55	4.798%	$253.1396	$253.14	$253.15	$253.10
Purchase #5	$91.39	10.501%	$100.9869	$100.99	$101.00	$101.00
Purchase #6	$178.78	9.803%	$196.3058	$196.31	$196.30	$196.30
Purchase #7	$47.40	10.614%	$52.431	$52.43	$52.45	$52.40
7 purchase totals =	$785.32		$843.3775	$843.38	$843.40	$843.30