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	$160.37	8.516%	$174.0271	$174.03	$174.05	$174.00
Purchase #2	$19.85	7.358%	$21.3106	$21.31	$21.30	$21.30
Purchase #3	$199.51	6.210%	$211.8996	$211.90	$211.90	$211.90
Purchase #4	$69.96	12.348%	$78.5987	$78.60	$78.60	$78.60
Purchase #5	$130.85	6.594%	$139.4782	$139.48	$139.50	$139.50
Purchase #6	$228.65	4.332%	$238.5551	$238.56	$238.55	$238.60
Purchase #7	$245.69	7.552%	$264.2445	$264.24	$264.25	$264.20
7 purchase totals =	$1,054.88		$1,128.1138	$1,128.12	$1,128.15	$1,128.10