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	$86.84	3.436%	$89.8238	$89.82	$89.80	$89.80
Purchase #2	$164.65	10.722%	$182.3038	$182.30	$182.30	$182.30
Purchase #3	$206.80	10.865%	$229.2688	$229.27	$229.25	$229.30
Purchase #4	$240.33	13.580%	$272.9668	$272.97	$272.95	$273.00
Purchase #5	$116.53	9.507%	$127.6085	$127.61	$127.60	$127.60
Purchase #6	$112.88	13.160%	$127.735	$127.74	$127.75	$127.70
Purchase #7	$107.32	7.535%	$115.4066	$115.41	$115.40	$115.40
7 purchase totals =	$1,035.35		$1,145.1133	$1,145.12	$1,145.05	$1,145.10