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	$101.83	3.667%	$105.5641	$105.56	$105.55	$105.60
Purchase #2	$245.77	12.527%	$276.5576	$276.56	$276.55	$276.60
Purchase #3	$241.82	11.352%	$269.2714	$269.27	$269.25	$269.30
Purchase #4	$62.54	9.269%	$68.3368	$68.34	$68.35	$68.30
Purchase #5	$167.81	12.580%	$188.9205	$188.92	$188.90	$188.90
Purchase #6	$160.43	6.222%	$170.412	$170.41	$170.40	$170.40
Purchase #7	$181.90	7.772%	$196.0373	$196.04	$196.05	$196.00
7 purchase totals =	$1,162.10		$1,275.0997	$1,275.10	$1,275.05	$1,275.10