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	$122.27	11.575%	$136.4228	$136.42	$136.40	$136.40
Purchase #2	$115.50	13.647%	$131.2623	$131.26	$131.25	$131.30
Purchase #3	$239.74	3.830%	$248.922	$248.92	$248.90	$248.90
Purchase #4	$168.62	12.167%	$189.136	$189.14	$189.15	$189.10
Purchase #5	$36.52	6.305%	$38.8226	$38.82	$38.80	$38.80
Purchase #6	$12.65	5.195%	$13.3072	$13.31	$13.30	$13.30
Purchase #7	$249.49	4.757%	$261.3582	$261.36	$261.35	$261.40
7 purchase totals =	$944.79		$1,019.2311	$1,019.23	$1,019.15	$1,019.20