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	$177.31	10.479%	$195.8903	$195.89	$195.90	$195.90
Purchase #2	$97.52	3.424%	$100.8591	$100.86	$100.85	$100.90
Purchase #3	$201.87	6.686%	$215.367	$215.37	$215.35	$215.40
Purchase #4	$105.74	5.303%	$111.3474	$111.35	$111.35	$111.30
Purchase #5	$106.56	12.326%	$119.6946	$119.69	$119.70	$119.70
Purchase #6	$220.73	13.284%	$250.0518	$250.05	$250.05	$250.10
Purchase #7	$212.74	13.206%	$240.8344	$240.83	$240.85	$240.80
7 purchase totals =	$1,122.47		$1,234.0446	$1,234.04	$1,234.05	$1,234.10