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	$221.63	7.792%	$238.8994	$238.90	$238.90	$238.90
Purchase #2	$20.45	7.448%	$21.9731	$21.97	$21.95	$22.00
Purchase #3	$243.48	5.754%	$257.4898	$257.49	$257.50	$257.50
Purchase #4	$79.88	10.517%	$88.281	$88.28	$88.30	$88.30
Purchase #5	$91.34	9.739%	$100.2356	$100.24	$100.25	$100.20
Purchase #6	$200.34	11.745%	$223.8699	$223.87	$223.85	$223.90
Purchase #7	$116.35	9.746%	$127.6895	$127.69	$127.70	$127.70
7 purchase totals =	$973.47		$1,058.4383	$1,058.44	$1,058.45	$1,058.50