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	$182.72	6.848%	$195.2327	$195.23	$195.25	$195.20
Purchase #2	$57.55	8.668%	$62.5384	$62.54	$62.55	$62.50
Purchase #3	$171.56	3.836%	$178.141	$178.14	$178.15	$178.10
Purchase #4	$39.35	7.786%	$42.4138	$42.41	$42.40	$42.40
Purchase #5	$145.27	13.302%	$164.5938	$164.59	$164.60	$164.60
Purchase #6	$37.44	8.340%	$40.5625	$40.56	$40.55	$40.60
Purchase #7	$55.85	12.347%	$62.7458	$62.75	$62.75	$62.70
7 purchase totals =	$689.74		$746.2280	$746.22	$746.25	$746.10