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	$170.92	8.275%	$185.0636	$185.06	$185.05	$185.10
Purchase #2	$156.35	6.596%	$166.6628	$166.66	$166.65	$166.70
Purchase #3	$117.86	7.839%	$127.099	$127.10	$127.10	$127.10
Purchase #4	$54.92	7.615%	$59.1022	$59.10	$59.10	$59.10
Purchase #5	$91.31	4.265%	$95.2044	$95.20	$95.20	$95.20
Purchase #6	$244.88	13.524%	$277.9976	$278.00	$278.00	$278.00
Purchase #7	$167.70	3.795%	$174.0642	$174.06	$174.05	$174.10
7 purchase totals =	$1,003.94		$1,085.1938	$1,085.18	$1,085.15	$1,085.30