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	$49.50	4.490%	$51.7226	$51.72	$51.70	$51.70
Purchase #2	$144.51	4.419%	$150.8959	$150.90	$150.90	$150.90
Purchase #3	$54.44	9.132%	$59.4115	$59.41	$59.40	$59.40
Purchase #4	$216.28	12.361%	$243.0144	$243.01	$243.00	$243.00
Purchase #5	$245.92	7.600%	$264.6099	$264.61	$264.60	$264.60
Purchase #6	$233.25	11.865%	$260.9251	$260.93	$260.95	$260.90
Purchase #7	$133.39	10.449%	$147.3279	$147.33	$147.35	$147.30
7 purchase totals =	$1,077.29		$1,177.9073	$1,177.91	$1,177.90	$1,177.80