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	$191.81	6.813%	$204.878	$204.88	$204.90	$204.90
Purchase #2	$172.38	13.773%	$196.1219	$196.12	$196.10	$196.10
Purchase #3	$215.52	8.131%	$233.0439	$233.04	$233.05	$233.00
Purchase #4	$109.30	7.836%	$117.8647	$117.86	$117.85	$117.90
Purchase #5	$101.35	9.432%	$110.9093	$110.91	$110.90	$110.90
Purchase #6	$245.88	12.378%	$276.315	$276.32	$276.30	$276.30
Purchase #7	$45.66	11.103%	$50.7296	$50.73	$50.75	$50.70
7 purchase totals =	$1,081.90		$1,189.8624	$1,189.86	$1,189.85	$1,189.80