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	$41.49	10.697%	$45.9282	$45.93	$45.95	$45.90
Purchase #2	$146.25	4.146%	$152.3135	$152.31	$152.30	$152.30
Purchase #3	$157.57	4.641%	$164.8828	$164.88	$164.90	$164.90
Purchase #4	$180.73	10.747%	$200.1531	$200.15	$200.15	$200.20
Purchase #5	$210.63	13.349%	$238.747	$238.75	$238.75	$238.70
Purchase #6	$155.29	12.635%	$174.9109	$174.91	$174.90	$174.90
Purchase #7	$243.69	6.213%	$258.8305	$258.83	$258.85	$258.80
7 purchase totals =	$1,135.65		$1,235.7660	$1,235.76	$1,235.80	$1,235.70