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	$121.36	5.326%	$127.8236	$127.82	$127.80	$127.80
Purchase #2	$238.98	4.566%	$249.8918	$249.89	$249.90	$249.90
Purchase #3	$19.50	3.404%	$20.1638	$20.16	$20.15	$20.20
Purchase #4	$43.94	5.155%	$46.2051	$46.21	$46.20	$46.20
Purchase #5	$196.32	9.637%	$215.2394	$215.24	$215.25	$215.20
Purchase #6	$244.74	5.710%	$258.7147	$258.71	$258.70	$258.70
Purchase #7	$219.92	12.836%	$248.1489	$248.15	$248.15	$248.10
7 purchase totals =	$1,084.76		$1,166.1873	$1,166.18	$1,166.15	$1,166.10