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	$139.50	6.138%	$148.0625	$148.06	$148.05	$148.10
Purchase #2	$144.29	5.632%	$152.4164	$152.42	$152.40	$152.40
Purchase #3	$75.29	4.149%	$78.4138	$78.41	$78.40	$78.40
Purchase #4	$232.91	8.565%	$252.8587	$252.86	$252.85	$252.90
Purchase #5	$241.69	9.415%	$264.4451	$264.45	$264.45	$264.40
Purchase #6	$202.82	9.136%	$221.3496	$221.35	$221.35	$221.30
Purchase #7	$210.93	4.254%	$219.903	$219.90	$219.90	$219.90
7 purchase totals =	$1,247.43		$1,337.4491	$1,337.45	$1,337.40	$1,337.40