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	$154.86	13.667%	$176.0247	$176.02	$176.00	$176.00
Purchase #2	$231.91	13.568%	$263.3755	$263.38	$263.40	$263.40
Purchase #3	$93.57	7.219%	$100.3248	$100.32	$100.30	$100.30
Purchase #4	$153.62	7.220%	$164.7114	$164.71	$164.70	$164.70
Purchase #5	$103.90	5.138%	$109.2384	$109.24	$109.25	$109.20
Purchase #6	$150.26	12.425%	$168.9298	$168.93	$168.95	$168.90
Purchase #7	$174.39	3.260%	$180.0751	$180.08	$180.10	$180.10
7 purchase totals =	$1,062.51		$1,162.6797	$1,162.68	$1,162.70	$1,162.60