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	$94.87	5.262%	$99.8621	$99.86	$99.85	$99.90
Purchase #2	$7.48	5.356%	$7.8806	$7.88	$7.90	$7.90
Purchase #3	$135.78	11.307%	$151.1326	$151.13	$151.15	$151.10
Purchase #4	$127.57	11.802%	$142.6258	$142.63	$142.65	$142.60
Purchase #5	$198.72	5.384%	$209.4191	$209.42	$209.40	$209.40
Purchase #6	$47.82	7.399%	$51.3582	$51.36	$51.35	$51.40
Purchase #7	$101.68	4.735%	$106.4945	$106.49	$106.50	$106.50
7 purchase totals =	$713.92		$768.7729	$768.77	$768.80	$768.80