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	$215.88	13.504%	$245.0324	$245.03	$245.05	$245.00
Purchase #2	$82.32	9.312%	$89.9856	$89.99	$90.00	$90.00
Purchase #3	$130.45	8.808%	$141.94	$141.94	$141.95	$141.90
Purchase #4	$181.53	8.362%	$196.7095	$196.71	$196.70	$196.70
Purchase #5	$50.92	10.135%	$56.0807	$56.08	$56.10	$56.10
Purchase #6	$192.91	10.327%	$212.8318	$212.83	$212.85	$212.80
Purchase #7	$133.72	9.396%	$146.2843	$146.28	$146.30	$146.30
7 purchase totals =	$987.73		$1,088.8643	$1,088.86	$1,088.95	$1,088.80