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	$99.69	11.370%	$111.0248	$111.02	$111.00	$111.00
Purchase #2	$39.61	8.705%	$43.0581	$43.06	$43.05	$43.10
Purchase #3	$151.33	9.600%	$165.8577	$165.86	$165.85	$165.90
Purchase #4	$195.66	11.809%	$218.7655	$218.77	$218.75	$218.80
Purchase #5	$22.59	11.391%	$25.1632	$25.16	$25.15	$25.20
Purchase #6	$87.96	4.823%	$92.2023	$92.20	$92.20	$92.20
Purchase #7	$177.82	11.515%	$198.296	$198.30	$198.30	$198.30
7 purchase totals =	$774.66		$854.3676	$854.37	$854.30	$854.50