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	$166.78	3.326%	$172.3271	$172.33	$172.35	$172.30
Purchase #2	$86.29	3.115%	$88.9779	$88.98	$89.00	$89.00
Purchase #3	$242.94	9.168%	$265.2127	$265.21	$265.20	$265.20
Purchase #4	$47.68	7.774%	$51.3866	$51.39	$51.40	$51.40
Purchase #5	$233.49	12.705%	$263.1549	$263.15	$263.15	$263.20
Purchase #6	$179.37	6.437%	$190.916	$190.92	$190.90	$190.90
Purchase #7	$29.37	3.179%	$30.3037	$30.30	$30.30	$30.30
7 purchase totals =	$985.92		$1,062.2789	$1,062.28	$1,062.30	$1,062.30