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	$162.43	6.433%	$172.8791	$172.88	$172.90	$172.90
Purchase #2	$47.54	12.342%	$53.4074	$53.41	$53.40	$53.40
Purchase #3	$52.76	3.613%	$54.6662	$54.67	$54.65	$54.70
Purchase #4	$128.84	5.260%	$135.617	$135.62	$135.60	$135.60
Purchase #5	$233.86	11.866%	$261.6098	$261.61	$261.60	$261.60
Purchase #6	$105.27	3.837%	$109.3092	$109.31	$109.30	$109.30
Purchase #7	$192.41	10.528%	$212.6669	$212.67	$212.65	$212.70
7 purchase totals =	$923.11		$1,000.1556	$1,000.17	$1,000.10	$1,000.20