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	$154.57	11.199%	$171.8803	$171.88	$171.90	$171.90
Purchase #2	$18.79	3.498%	$19.4473	$19.45	$19.45	$19.40
Purchase #3	$169.56	9.119%	$185.0222	$185.02	$185.00	$185.00
Purchase #4	$124.52	5.226%	$131.0274	$131.03	$131.05	$131.00
Purchase #5	$120.85	12.856%	$136.3865	$136.39	$136.40	$136.40
Purchase #6	$94.87	10.512%	$104.8427	$104.84	$104.85	$104.80
Purchase #7	$101.29	3.366%	$104.6994	$104.70	$104.70	$104.70
7 purchase totals =	$784.45		$853.3058	$853.31	$853.35	$853.20