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	$78.41	5.613%	$82.8112	$82.81	$82.80	$82.80
Purchase #2	$244.92	8.526%	$265.8019	$265.80	$265.80	$265.80
Purchase #3	$115.66	13.353%	$131.1041	$131.10	$131.10	$131.10
Purchase #4	$236.32	3.361%	$244.2627	$244.26	$244.25	$244.30
Purchase #5	$157.86	10.318%	$174.148	$174.15	$174.15	$174.10
Purchase #6	$30.46	11.547%	$33.9772	$33.98	$34.00	$34.00
Purchase #7	$249.72	5.824%	$264.2637	$264.26	$264.25	$264.30
7 purchase totals =	$1,113.35		$1,196.3688	$1,196.36	$1,196.35	$1,196.40