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	$86.94	3.463%	$89.9507	$89.95	$89.95	$90.00
Purchase #2	$193.43	11.486%	$215.6474	$215.65	$215.65	$215.60
Purchase #3	$242.77	10.125%	$267.3505	$267.35	$267.35	$267.40
Purchase #4	$146.31	3.119%	$150.8734	$150.87	$150.85	$150.90
Purchase #5	$114.49	11.474%	$127.6266	$127.63	$127.65	$127.60
Purchase #6	$103.74	13.132%	$117.3631	$117.36	$117.35	$117.40
Purchase #7	$42.66	6.231%	$45.3181	$45.32	$45.30	$45.30
7 purchase totals =	$930.34		$1,014.1298	$1,014.13	$1,014.10	$1,014.20