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	$115.50	10.250%	$127.3388	$127.34	$127.35	$127.30
Purchase #2	$90.38	9.578%	$99.0366	$99.04	$99.05	$99.00
Purchase #3	$125.69	12.283%	$141.1285	$141.13	$141.15	$141.10
Purchase #4	$241.53	9.666%	$264.8763	$264.88	$264.90	$264.90
Purchase #5	$116.52	9.479%	$127.5649	$127.56	$127.55	$127.60
Purchase #6	$126.60	9.263%	$138.327	$138.33	$138.35	$138.30
Purchase #7	$236.44	13.343%	$267.9882	$267.99	$268.00	$268.00
7 purchase totals =	$1,052.66		$1,166.2603	$1,166.27	$1,166.35	$1,166.20