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	$152.91	10.136%	$168.409	$168.41	$168.40	$168.40
Purchase #2	$96.43	7.174%	$103.3479	$103.35	$103.35	$103.30
Purchase #3	$190.51	13.169%	$215.5983	$215.60	$215.60	$215.60
Purchase #4	$62.92	4.451%	$65.7206	$65.72	$65.70	$65.70
Purchase #5	$156.26	9.738%	$171.4766	$171.48	$171.50	$171.50
Purchase #6	$127.25	11.818%	$142.2884	$142.29	$142.30	$142.30
Purchase #7	$16.81	9.427%	$18.3947	$18.39	$18.40	$18.40
7 purchase totals =	$803.09		$885.2355	$885.24	$885.25	$885.20