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	$59.73	9.285%	$65.2759	$65.28	$65.30	$65.30
Purchase #2	$28.79	5.192%	$30.2848	$30.28	$30.30	$30.30
Purchase #3	$240.46	11.102%	$267.1559	$267.16	$267.15	$267.20
Purchase #4	$165.60	5.105%	$174.0539	$174.05	$174.05	$174.10
Purchase #5	$29.61	6.433%	$31.5148	$31.51	$31.50	$31.50
Purchase #6	$98.75	4.840%	$103.5295	$103.53	$103.55	$103.50
Purchase #7	$215.38	8.324%	$233.3082	$233.31	$233.30	$233.30
7 purchase totals =	$838.32		$905.1230	$905.12	$905.15	$905.20