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	$41.81	8.391%	$45.3183	$45.32	$45.30	$45.30
Purchase #2	$240.38	11.286%	$267.5093	$267.51	$267.50	$267.50
Purchase #3	$145.31	6.505%	$154.7624	$154.76	$154.75	$154.80
Purchase #4	$130.60	8.837%	$142.1411	$142.14	$142.15	$142.10
Purchase #5	$165.66	3.449%	$171.3736	$171.37	$171.35	$171.40
Purchase #6	$97.27	5.283%	$102.4088	$102.41	$102.40	$102.40
Purchase #7	$157.89	5.336%	$166.315	$166.32	$166.30	$166.30
7 purchase totals =	$978.92		$1,049.8285	$1,049.83	$1,049.75	$1,049.80