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	$152.27	12.635%	$171.5093	$171.51	$171.50	$171.50
Purchase #2	$201.46	6.790%	$215.1391	$215.14	$215.15	$215.10
Purchase #3	$19.32	7.769%	$20.821	$20.82	$20.80	$20.80
Purchase #4	$93.38	3.123%	$96.2963	$96.30	$96.30	$96.30
Purchase #5	$11.96	12.263%	$13.4267	$13.43	$13.45	$13.40
Purchase #6	$128.40	4.286%	$133.9032	$133.90	$133.90	$133.90
Purchase #7	$56.28	11.292%	$62.6351	$62.64	$62.65	$62.60
7 purchase totals =	$663.07		$713.7307	$713.74	$713.75	$713.60