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	$31.89	6.792%	$34.056	$34.06	$34.05	$34.10
Purchase #2	$84.46	5.492%	$89.0985	$89.10	$89.10	$89.10
Purchase #3	$173.95	3.297%	$179.6851	$179.69	$179.70	$179.70
Purchase #4	$201.92	10.104%	$222.322	$222.32	$222.30	$222.30
Purchase #5	$71.29	8.474%	$77.3311	$77.33	$77.35	$77.30
Purchase #6	$16.31	12.312%	$18.3181	$18.32	$18.30	$18.30
Purchase #7	$175.92	11.551%	$196.2405	$196.24	$196.25	$196.20
7 purchase totals =	$755.74		$817.0513	$817.06	$817.05	$817.00