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	$173.96	10.562%	$192.3337	$192.33	$192.35	$192.30
Purchase #2	$40.41	5.839%	$42.7695	$42.77	$42.75	$42.80
Purchase #3	$153.83	4.352%	$160.5247	$160.52	$160.50	$160.50
Purchase #4	$98.65	11.257%	$109.755	$109.76	$109.75	$109.80
Purchase #5	$127.70	8.757%	$138.8827	$138.88	$138.90	$138.90
Purchase #6	$152.53	12.461%	$171.5368	$171.54	$171.55	$171.50
Purchase #7	$176.64	13.738%	$200.9068	$200.91	$200.90	$200.90
7 purchase totals =	$923.72		$1,016.7092	$1,016.71	$1,016.70	$1,016.70