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	$40.28	4.359%	$42.0358	$42.04	$42.05	$42.00
Purchase #2	$244.42	4.502%	$255.4238	$255.42	$255.40	$255.40
Purchase #3	$109.36	5.598%	$115.482	$115.48	$115.50	$115.50
Purchase #4	$5.66	11.335%	$6.3016	$6.30	$6.30	$6.30
Purchase #5	$9.72	3.554%	$10.0654	$10.07	$10.05	$10.10
Purchase #6	$56.73	5.450%	$59.8218	$59.82	$59.80	$59.80
Purchase #7	$183.92	11.765%	$205.5582	$205.56	$205.55	$205.60
7 purchase totals =	$650.09		$694.6886	$694.69	$694.65	$694.70