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	$250.71	4.176%	$261.1796	$261.18	$261.20	$261.20
Purchase #2	$64.72	11.839%	$72.3822	$72.38	$72.40	$72.40
Purchase #3	$215.89	4.708%	$226.0541	$226.05	$226.05	$226.10
Purchase #4	$250.50	10.812%	$277.5841	$277.58	$277.60	$277.60
Purchase #5	$52.62	8.802%	$57.2516	$57.25	$57.25	$57.30
Purchase #6	$224.46	8.365%	$243.2361	$243.24	$243.25	$243.20
Purchase #7	$115.31	10.274%	$127.1569	$127.16	$127.15	$127.20
7 purchase totals =	$1,174.21		$1,264.8446	$1,264.84	$1,264.90	$1,265.00