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	$73.36	7.206%	$78.6463	$78.65	$78.65	$78.60
Purchase #2	$83.34	6.804%	$89.0105	$89.01	$89.00	$89.00
Purchase #3	$102.93	11.609%	$114.8791	$114.88	$114.90	$114.90
Purchase #4	$32.70	6.693%	$34.8886	$34.89	$34.90	$34.90
Purchase #5	$30.29	12.647%	$34.1208	$34.12	$34.10	$34.10
Purchase #6	$209.45	4.738%	$219.3737	$219.37	$219.35	$219.40
Purchase #7	$166.58	8.654%	$180.9958	$181.00	$181.00	$181.00
7 purchase totals =	$698.65		$751.9148	$751.92	$751.90	$751.90