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	$198.42	5.499%	$209.3311	$209.33	$209.35	$209.30
Purchase #2	$117.51	11.825%	$131.4056	$131.41	$131.40	$131.40
Purchase #3	$165.99	6.821%	$177.3122	$177.31	$177.30	$177.30
Purchase #4	$81.33	9.610%	$89.1458	$89.15	$89.15	$89.10
Purchase #5	$56.82	9.674%	$62.3168	$62.32	$62.30	$62.30
Purchase #6	$89.86	12.678%	$101.2525	$101.25	$101.25	$101.30
Purchase #7	$160.93	10.147%	$177.2596	$177.26	$177.25	$177.30
7 purchase totals =	$870.86		$948.0236	$948.03	$948.00	$948.00